Devices for overvoltage, overcurrent and arc flash protection

ABSTRACT

A crowbar module includes first and second electrical terminals, a module housing, and first and second crowbar units. The first crowbar unit is disposed in the module housing and includes a first thyristor electrically connected between the first and second electrical terminals. The second crowbar unit is disposed in the module housing and includes a second thyristor electrically connected between the first and second electrical terminals in electrical parallel with the first crowbar unit.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/578,779, filed Sep. 23, 2019, which is a continuation ofU.S. patent application Ser. No. 15/071,758, now U.S. Pat. No.10,447,023 filed Mar. 16, 2016, which claims the benefit of and priorityfrom U.S. Provisional Patent Application No. 62/135,284, filed Mar. 19,2015, the disclosures of each are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to circuit protection devices and, moreparticularly, to overvoltage, overcurrent and arc flash protectiondevices and methods.

BACKGROUND

Frequently, excessive voltage or current is applied across service linesthat deliver power to residences and commercial and institutionalfacilities. Such excess voltage or current spikes (transientovervoltages and surge currents) may result from lightning strikes, forexample. The above events may be of particular concern intelecommunications distribution centers, hospitals and other facilitieswhere equipment damage caused by overvoltages and/or current surges andresulting down time may be very costly.

Typically, sensitive electronic equipment may be protected againsttransient overvoltages and surge currents using Surge Protective Devices(SPDs). For example, brief reference is made to FIG. 1 , which is asystem including conventional overvoltage and surge protection. Anovervoltage protection device 10 may be installed at a power input ofequipment to be protected 50, which is typically protected againstovercurrents. Typical failure mode of an SPD is a short circuit. Theovercurrent protection typically employed is a combination of aninternal thermal disconnector to protect the device from overheating dueto increased leakage currents and an external fuse to protect the devicefrom higher fault currents. Different SPD technologies may avoid the useof the internal thermal disconnector because, in the event of failure,they change their operation mode to a low ohmic resistance. In thismanner, the device can withstand significant short circuit currents. Inthis regard, there may be no operational need for an internal thermaldisconnector. Further to the above, some embodiments that exhibit evenhigher short circuit withstand capabilities may also be protected onlyby the main circuit breaker of the installation without the need for adedicated branch fuse.

Brief reference is now made to FIG. 2 , which is a block diagram of asystem including conventional surge protection. As illustrated, a threephase line may be connected to and supply electrical energy to one ormore transformers 66, which may in turn supply three phase electricalpower to a main circuit breaker 68. The three phase electrical power maybe provided to one or more distribution panels 62. As illustrated, thethree voltage lines of the three phase electrical power may designatedas L1, L2 and L3 and a neutral line may be designated as N. In someembodiments, the neutral line N may be conductively coupled to an earthground.

Some embodiments include surge protection devices (SPDs) 104. Asillustrated, each of the SPDs 104 may be connected between respectiveones of L1, L2 and L3, and neutral (N). The SPD 104 may protect otherequipment in the installation such as the distribution panel amongothers. In addition, the SPDs may be used to protect all equipment incase of prolonged overvoltages. However, such a condition may force theSPD to conduct a limited current for a prolonged period of time, whichmay result in the overheating of the SPD and possibly its failure(depending on the energy withstand capabilities the SPD can absorb andthe level and duration of the overvoltage condition). A typicaloperating voltage of an SPD 104 in the present example may be about 400V(for 690V L-L systems). In this regard, the SPDs 104 will each performas an insulator and thus not conduct current during normal operatingconditions. In some embodiments, the operating voltage of the SPD's 104is sufficiently higher than the normal line-to-neutral voltage to ensurethat the SPD 104 will continue to perform as an insulator even in casesin which the system voltage increases due to overvoltage conditions thatmight arise as a result of a loss of power or other power system issues.

In the event of a surge current in, for example, L1, protection of powersystem load devices may necessitate providing a current path to groundfor the excess current of the surge current. The surge current maygenerate a transient overvoltage between L1 and N. Since the transientovervoltage significantly exceeds that operating voltage of SPD 104, theSPD 104 will become conductive, allowing the excess current to flow fromL1 through SPD 104 to the neutral N. Once the surge current has beenconducted to N, the overvoltage condition ends and the SPD 104 maybecome non-conducting again. However, in some cases, one or more SPD's104 may begin to allow a leakage current to be conducted even atvoltages that are lower that the operating voltage of the SPD's 104.

Additionally, within an electrical device cabinet there may be devicesthat may protect the equipment inside the cabinet and proximatepersonnel from arc flashes that could be generated inside the cabinet.An arc flash occurring within a cabinet may create severe damages and isconsidered to be a very serious safety hazard for the personnel. Assuch, detection of the arc flash and interruption of the correspondingcurrent should be as fast as possible to minimize damages and/or risks.However, especially in high power systems, during an arc flash the faultcurrent could be limited to a lower level than the current thresholdrequired for the main circuit breaker to trip fast enough. Fasterresponse times may be required to avoid damages and/or risk. Onesolution employed by many manufacturers includes an electronic system toforce the external tripping of the circuit breaker. During an arc flashthere may be a significant increase of the pressure inside the cabinetand a significant increase in the illumination. An electronic circuitmay use pressure and/or optical sensors to detect the presence of an arcflash and trip the circuit breaker. Other more recent techniques usereadings of the voltage and current of the power system and trip thecircuit breaker when specific patterns of these readings areencountered.

However, the time that a circuit breaker may take to disconnect thesystem form the power source (after being externally tripped by theelectronic circuit) may be in the order of 100 milliseconds or more.During this time, a short circuit current that may be in a range ofabout 10 kAmperes to about 100 kAmperes may cause damage to the internalportions of the equipment as well as expose proximate personnel tosignificant danger.

SUMMARY

Some embodiments of the present invention are directed to a circuitprotection device that includes an arc flash, overcurrent, overvoltageand surge protection system that is connected between a plurality ofphase lines and a neutral line that are between an incoming power supplyline and an electrical load panel in an electrical equipment.

In some embodiments, the arc flash, overcurrent, overvoltage and surgeprotection system includes a crowbar device that is coupled to theplurality of phase lines and to the neutral line and is configured toprevent an overvoltage condition by generating a low resistance currentpath from the plurality of phase lines to the neutral line, a pluralityof surge protection devices that are connected to the plurality of phaselines and to the neutral line and that are configured to protect theequipment during an overvoltage condition by conducting a limited amountof current that corresponds to the overvoltage condition, and a crowbartrigger circuit that is configured to cause the crowbar device to turnon and provide the low resistance current path from ones of theplurality of phase lines to the neutral line.

Some embodiments provide that the crowbar device includes a plurality ofovervoltage protection modules that are coupled between respective onesof the plurality of phase lines and the neutral line. In someembodiments, ones of the plurality of overvoltage protection moduleseach include a bidirectional thyristor and an inductor that is connectedin series with the bidirectional thyristor. Some embodiments providethat ones of the plurality of overvoltage protection modules eachinclude two thyristors that are connected in antiparallel with oneanother and an inductor that is connected in series with the twothyristors. In some embodiments, the ones of the plurality ofovervoltage modules further comprise a snubber circuit that is connectedin parallel with the two thyristors. Some embodiments provide that thesnubber circuit includes a resistor and a capacitor that are connectedin series with one another.

In some embodiments, the arc flash, overcurrent, overvoltage and surgeprotection system further includes an arc flash detection system that isconfigured to detect an arc flash within the equipment and to generateand send an arc flash signal to the crowbar trigger circuit.

Some embodiments provide that the crowbar trigger circuit includes aplurality of thyristor trigger circuits that are configured to generatethyristor trigger signals that are received by the crowbar device. Insome embodiments, the crowbar trigger circuit further includes a powersupply and voltage hold-up circuit that is configured to receiveelectrical power for the trigger circuit and to provide power to thetrigger circuit for a time period after the electrical power for thetrigger circuit is lost, an interface circuit that is configured toreceive inputs corresponding to voltages of the plurality of phaselines, current flow through the plurality of phase lines, an arc flashsignal and/or temperatures or respective surge protection devices, and amicrocontroller that is configured to receive data from the interfacecircuit, to process the received data and to generate and send triggersignals one or more of the plurality of thyristor trigger circuits, analarm signal to a remote alerting device and/or a trip signal to a maincircuit breaker. Some embodiments provide that the power supply andvoltage holdup circuit includes a plurality of DC-DC converters that areeach operable to provide voltages to ones of the plurality of thyristortrigger circuits and a holdup circuit that is configured to hold avoltage that is provided to the plurality of DC-dc converters.

Some embodiments provide that the crowbar device includes a plurality ofpairs of antiparallel connected thyristors that are coupled betweenrespective ones of the plurality of phase lines and the neutral line, aplurality of inductors that are connected in series respective ones ofthe plurality of pairs of antiparallel thyristors, and a plurality ofsurge protection devices that are connected between respective ones ofthe plurality of phase lines and the neutral line.

In some embodiments, the arc flash, overcurrent, overvoltage and surgeprotection system includes a crowbar device that is coupled to andbetween the plurality of phase lines and is configured to prevent anovervoltage condition by selectively generating a low resistance currentpath between the plurality of phase lines, a plurality of surgeprotection devices that are connected to and between the plurality ofphase lines and that are configured to protect the equipment during anovervoltage condition by conducting a limited amount of current thatcorresponds to the overvoltage condition, and a crowbar trigger circuitthat is configured to cause the crowbar device to turn on and providethe low resistance current path from ones of the plurality of phaselines to the neutral line.

Some embodiments provide that the arc flash, overcurrent, overvoltageand surge protection system includes a crowbar device that is coupled tothe plurality of phase lines and to the neutral line and is configuredto prevent an overvoltage condition by generating a low resistancecurrent path from the plurality of phase lines to the neutral line, aplurality of surge protection devices that are connected to theplurality of phase lines and to the neutral line and that are configuredto protect the equipment during an overvoltage condition by conducting alimited amount of current that corresponds to the overvoltage condition,and an arc flash trigger circuit that is configured to cause the crowbardevice to turn on and provide the low resistance current path from onesof the plurality of phase lines to the neutral line. In someembodiments, the crowbar device includes a plurality of self-triggeringcrowbar modules that are connected to the neutral line and respectiveones of the plurality of phase lines.

In some embodiments, the plurality of self-triggering crowbar moduleseach include two thyristors that are connected in antiparallel with oneanother, an inductor that is connected in series with the twothyristors, and a crowbar trigger circuit that is configured to receivea current signal from a current sensor on the corresponding one of theplurality of phase lines and to cause at least one of the two thyristorsto provide a low resistance current path between the corresponding oneof the plurality of phase lines and the neutral line responsive to thecurrent signal exceeding a current threshold.

In some embodiments, the crowbar trigger circuit is configured togenerate a trigger signal in the absence of any signal from the arcflash trigger circuit. Some embodiments provide that the crowbar triggercircuit is configured to provide self triggering of the correspondingone of the plurality of crowbar modules during a start-up period of theequipment. In some embodiments, the arc flash trigger circuit isconfigured to trigger the plurality of crowbar modules responsive todetecting an arc flash after the start-up period of the equipment.

Some embodiments provide that the ones of the plurality of crowbarmodules further include a snubber circuit that is connected in parallelwith the two thyristors and that the snubber circuit includes a resistorand a capacitor that are connected in series with one another.

In some embodiments, the arc flash, overcurrent, overvoltage and surgeprotection system further includes an arc flash detection system that isconfigured to detect an arc flash within the equipment and to generateand send an arc flash signal to the arc flash trigger circuit.

Some embodiments provide that the arc flash, overcurrent, overvoltageand surge protection system further includes a threshold selector thatis connected to the arc flash trigger circuit and is configured toprovide a threshold current selection signal corresponding to a currentthreshold value. In some embodiments, the threshold selector includes auser input device that receives a user input and that provides thethreshold current selection signal to the arc flash trigger circuit.Some embodiments provide that the threshold current selection signalincludes a discrete binary value, and wherein a lowest value of thediscrete binary value corresponds to a default threshold current.

Some embodiments of the present invention are directed to an arc flash,overcurrent, overvoltage and surge protection system that includes acrowbar device that is coupled to and between a plurality of phase linesand is configured to prevent an overvoltage condition by selectivelygenerating a low resistance current path between the plurality of phaselines and a plurality of surge protection devices that are connected torespective ones of the plurality of phase lines and to the crowbardevice and that are configured to protect the equipment during anovervoltage condition by conducting a limited amount of current thatcorresponds to the overvoltage condition.

In some embodiments, ones of the plurality of surge protection deviceseach include a first terminal that is connected to a corresponding oneof the plurality of phase lines and a second terminal that is connectedto the crowbar device. Some embodiments provide that the crowbar deviceincludes a plurality of phase terminals that are connected to theplurality of surge protection devices and a plurality of thyristors thatare connected between different pairs of the phase terminals.

Some embodiments provide that the crowbar device further includes acrowbar trigger circuit that is operable to generate thyristor triggersignals to the plurality of thyristors responsive to detecting a faultcondition on the phase lines. In some embodiments, the crowbar triggercircuit includes a rectification circuit that generates a direct current(DC) signal corresponding to the voltages between the plurality of phaselines, a comparator that compares the DC signal from the rectificationcircuit to a reference signal, and a plurality of isolation drivers thatreceive a comparator output, and, responsive to the comparator outputindicating that the DC signal exceeds the reference signal, generates atrigger signal that turns on the plurality of thyristors.

In some embodiments, the surge protection devices comprise metal oxidevaristors.

Some embodiments of the present invention are directed to a surgeprotection system that includes a plurality of crowbar modules that arecoupled to a plurality of phase lines and that are configured to preventan overvoltage condition by selectively generating a low resistancecurrent path between the plurality of phase lines and a neutral line anda plurality of surge protection devices that are connected in serieswith respective ones of the plurality of crowbar modules to provide aplurality of series circuits that each include one of the plurality ofcrowbar modules and one of the plurality of surge protection devices,wherein each of series circuits is connected between a corresponding oneof the plurality of phase lines and the neutral line.

In some embodiments, ones of the plurality of surge protection deviceseach include a first terminal that is connected to a corresponding oneof the plurality of phase lines and a second terminal that is connectedto a corresponding one of the plurality of crowbar modules. In someembodiments, ones of the plurality of crowbar modules each include aplurality of antiparallel thyristors that are connected between acorresponding one of the plurality of surge protection devices and theneutral line and a crowbar trigger circuit that is operable to generatethyristor trigger signals to the plurality of thyristors responsive todetecting a fault condition on the phase lines.

In some embodiments, the crowbar trigger circuit includes arectification circuit that generates a direct current (DC) signalcorresponding to a voltage on the corresponding one of the plurality ofphase lines, a comparator that compares the DC signal from therectification circuit to a reference signal, a driver that receives thecomparator output, and, responsive to the comparator output indicatingthat the DC signal exceeds the reference signal, generates a thyristordrive signal, and an optical isolator that generates a thyristor triggersignal responsive to receiving the thyristor drive signal from thedriver, wherein the thyristor trigger signal turns the pair ofantiparallel thyristors on to provide a low resistance current pathbetween the corresponding one of the surge protectors and the neutralline.

According to embodiments of the invention, a crowbar module includesfirst and second electrical terminals, a module housing, and first andsecond crowbar units. The first crowbar unit is disposed in the modulehousing and includes a first thyristor electrically connected betweenthe first and second electrical terminals. The second crowbar unit isdisposed in the module housing and includes a second thyristorelectrically connected between the first and second electrical terminalsin electrical parallel with the first crowbar unit.

In some embodiments, the first thyristor is connected in antiparallel tothe second thyristor.

The crowbar module may include a snubber circuit disposed in the modulehousing and electrically connected between the first and secondelectrical terminals in electrical parallel with each of the first andsecond crowbar units.

The crowbar module may include a coil assembly connected electrically inseries between the first terminal and each of the first and secondcrowbar units. In some embodiments, the crowbar module includes asnubber circuit disposed in the module housing and electricallyconnected between the first and second electrical terminals inelectrical parallel with each of the first and second crowbar units.

In some embodiments, the coil assembly includes: an electricallyconductive coil member, the coil member including a spirally extendingcoil strip defining a spiral coil channel; and an electricallyinsulating casing including a separator wall portion that fills the coilchannel.

In some embodiments, the module housing includes a cover defining anenclosed cavity, the first and second crowbar units are contained in theenclosed cavity, and the crowbar module further includes a fillermaterial that fills a volume in the enclosed cavity not occupied by thefirst and second crowbar units. In some embodiments, the filler materialis an epoxy.

The crowbar module may include a metal-oxide varistor device disposed inthe module housing and electrically connected between the first andsecond electrical terminals in parallel with each of the first andsecond crowbar units.

The crowbar module may include a trigger circuit disposed in the modulehousing and electrically connected to the first and second crowbarunits. In some embodiments, the crowbar module includes an electricalconnection to an external current sensor.

According to some embodiments, the first thyristor includes a firstcontact surface that is one of an anode and a cathode, and a secondcontact surface that is the other of an anode and a cathode, and thefirst crowbar unit includes an electrically conductive first electrodecontacting the first contact surface, and an electrically conductivesecond electrode contacting the second contact surface. In someembodiments, the first electrode is a unitary metal unit housing memberincluding an end wall and a side wall, the end wall and the side walldefine a unit housing cavity, the thyristor is disposed in the unithousing cavity. The crowbar module may include a biasing device biasingat least one of the first and second electrode members against the firstor second contact surface.

According to some embodiments, the first crowbar unit includes: a unithousing defining an enclosed chamber, the first thyristor being disposedin the enclosed chamber; a wire port defined in a wall of the unithousing between the enclosed chamber and an exterior of the unithousing; a cable gland mounted in the wire port; and an electrical leadextending through the cable gland from the exterior of the unit housingand electrically connected to the first thyristor.

The electrical lead wire may be terminated at a control terminal of thefirst thyristor. The crowbar module may include a second electrical leadwire extending through the cable gland from the exterior of the unithousing and electrically connected to a reference terminal of the firstthyristor.

In some embodiments, the cable gland is bonded to the electrical leadwire. In some embodiments, the cable gland includes a resin that isbonded to the electrical lead wire. In some embodiments, the resin is anepoxy resin.

According to some embodiments, the cable gland includes: a tubular outerfitting secured in the wire port; and a sealing plug mounted in theouter fitting and surrounding the electrical lead wire; wherein thesealing plug fills the radial space between the electrical lead wire andthe outer fitting. In some embodiments, the sealing plug is bonded tothe electrical lead wire. In some embodiments, the outer fitting isformed of a polymeric material bonded to the unit housing.

According to some embodiments, the cable gland mechanically secures theelectrical lead wire to the unit housing and hermetically seals the wireport.

According to embodiments of the invention, a crowbar unit includes aunit housing defining an enclosed chamber, a thyristor disposed in theenclosed chamber, a wire port defined in a wall of the unit housingbetween the enclosed chamber and an exterior of the unit housing, acable gland mounted in the wire port, and an electrical lead extendingthrough the cable gland from the exterior of the unit housing andelectrically connected to the thyristor.

In some embodiments, the thyristor includes a first contact surface thatis one of an anode and a cathode, and a second contact surface that isthe other of an anode and a cathode, and the crowbar unit includes anelectrically conductive first electrode contacting the first contactsurface, and an electrically conductive second electrode contacting thesecond contact surface.

According to some embodiments, the first electrode is a unitary metalhousing member including an end wall and a side wall, the housing memberforms a part of the unit housing and defines a housing cavity, and thethyristor is disposed in the housing cavity.

The crowbar unit may include a biasing device biasing at least one ofthe first and second electrode members against the first or secondcontact surface.

In some embodiments, the electrical lead wire is terminated at a controlterminal of the thyristor. The crowbar unit may include a secondelectrical lead wire extending through the cable gland from the exteriorof the unit housing and electrically connected to a reference terminalof the thyristor.

According to some embodiments, the cable gland is bonded to theelectrical lead wire. In some embodiments, the cable gland includes aresin that is bonded to the electrical lead wire. In some embodiments,the resin is an epoxy resin.

According to some embodiments, the cable gland includes a tubular outerfitting secured in the wire port, and a sealing plug mounted in theouter fitting and surrounding the electrical lead wire, wherein thesealing plug fills the radial space between the electrical lead wire andthe outer fitting. In some embodiments, the sealing plug is bonded tothe electrical lead wire. In some embodiments, the outer fitting isformed of a polymeric material bonded to the unit housing.

According to some embodiments, the cable gland mechanically secures theelectrical lead wire to the unit housing and hermetically seals the wireport.

In some embodiments, the thyristor is a bi-directional thyristor.

According to method embodiments of the invention, a method for forming acrowbar unit includes: providing a unit housing defining an enclosedchamber and including a wire port defined in a wall of the unit housingbetween the enclosed chamber and an exterior of the unit housing;mounting a thyristor in the enclosed chamber; routing an electrical leadwire through the wire port; sealing the electrical lead wire in the wireport with a cable gland; and electrically connecting the electrical leadwire to the thyristor.

In some embodiments, sealing the electrical lead wire in the wire portwith a cable gland includes: forming a cable gland, including insertingan electrical lead wire in a tubular outer fitting, introducing a liquidsealing material into the outer fitting about the electrical lead wire,and curing or hardening the liquid sealing material about the electricallead wire to seal the electrical lead wire in the outer fitting; andmounting the electrical lead wire and the cable gland in the wire port.In some embodiments, the liquid sealing material is a resin.

According to embodiments of the invention, a crowbar device includes adevice housing and a crowbar module and a current sensor disposed in thedevice housing. The crowbar module includes: a module housing; athyristor disposed in the module housing; a self-trigger circuitdisposed in the module housing; and a snubber circuit disposed in themodule housing.

According to embodiments of the invention, a crowbar system includes acrowbar module and an external trigger and alarm interface circuit. Thecrowbar module includes: a module housing; a thyristor disposed in themodule housing; a coil disposed in the module housing; a trigger circuitdisposed in the module housing; and a snubber circuit disposed in themodule housing. The external trigger and alarm interface circuit iselectrically connected to the crowbar module.

It is noted that aspects of the invention described with respect to oneembodiment, may be incorporated in a different embodiment although notspecifically described relative thereto. That is, all embodiments and/orfeatures of any embodiment can be combined in any way and/orcombination. These and other objects and/or aspects of the presentinvention are explained in detail in the specification set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures are included to provide a further understandingof the present invention, and are incorporated in and constitute a partof this specification. The drawings illustrate some embodiments of thepresent invention and, together with the description, serve to explainprinciples of the present invention.

FIG. 1 is a block diagram of a system including conventional surgeprotection.

FIG. 2 is a block diagram of a system including conventional surgeprotection.

FIG. 3 is a block diagram illustrating an arc flash and surge protectionsystem according to some embodiments of the present invention.

FIG. 4 is a block diagram illustrating an arc flash and surge protectionsystem according to some embodiments of the present invention.

FIG. 5 is a schematic diagram representing a circuit including an arcflash and surge protection system in a switchgear cabinet according tosome embodiments of the present invention.

FIG. 6 is a schematic block diagram illustrating a trigger circuit asbriefly described above regarding FIG. 4 , according to some embodimentsof the present invention.

FIG. 7 is a schematic block diagram illustrating a power supply andvoltage hold-up circuit as discussed in reference to FIG. 6 .

FIG. 8 is a block diagram illustrating a DC-DC isolated converter asdiscussed in reference to FIG. 7 .

FIG. 9 is a schematic block diagram illustrating a thyristor triggercircuit as discussed in reference to FIG. 6 .

FIG. 10 is a schematic diagram representing a circuit including an arcflash and surge protection system according to some embodiments of thepresent invention.

FIG. 11 is a schematic diagram representing a circuit including an arcflash and surge protection system according to some embodiments of thepresent invention.

FIG. 12 is a schematic diagram representing a circuit including an arcflash and surge protection system according to some embodiments of thepresent invention.

FIG. 13 is a top perspective view of a crowbar system and a triggermodule according to some embodiments of the present invention.

FIG. 14 is a cross-sectional view of the crowbar system of FIG. 13 takenalong the line 14-14 of FIG. 13 .

FIG. 15 is a top perspective view of a crowbar module forming a part ofthe crowbar system of FIG. 13 .

FIG. 16 is a fragmentary, exploded, top perspective view of the crowbarmodule of FIG. 15 .

FIG. 17 is an exploded, top perspective view of a coil assembly forminga part of the crowbar module of FIG. 15 .

FIG. 18 is a cross-sectional, bottom perspective view of a casingforming a part of the coil assembly of FIG. 17 .

FIG. 19 is an exploded, bottom perspective view of a crowbar unitforming a part of the crowbar module of FIG. 15 .

FIG. 20 is a cross-sectional, top perspective view of the crowbar unitof FIG. 19 .

FIG. 21 is an enlarged, fragmentary, cross-sectional view of the crowbarunit of FIG. 19 .

FIG. 22 is a rear perspective view of the connector module of FIG. 13 .

FIG. 23 is a fragmentary, perspective view of a crowbar module accordingto further embodiments of the invention.

FIG. 24 is a schematic diagram illustrating an arc flash and surgeprotection system used in protecting equipment according to someembodiments of the present invention.

FIG. 25 is a schematic block diagram illustrating a crowbar module asbriefly described above regarding FIG. 24 , according to someembodiments of the present invention.

FIG. 26 is a schematic block diagram illustrating a trigger circuit ofthe crowbar module as briefly described above regarding FIG. 25 ,according to some embodiments of the present invention.

FIG. 27 is a graph illustrating voltage and current values during anovervoltage condition according to some embodiments of the presentinvention.

FIG. 28 is a schematic block diagram illustrating an arc flash triggercircuit of the crowbar module as briefly described above regarding FIG.24 , according to some embodiments of the present invention.

FIG. 29 is a schematic block diagram illustrating a surge protectionsystem used in protecting equipment according to some embodiments of thepresent invention.

FIG. 30 is a schematic block diagram illustrating a crowbar device asbriefly described above regarding FIG. 29 , according to someembodiments of the present invention.

FIG. 31 is a schematic block diagram illustrating a surge protectionsystem used in protecting equipment according to some embodiments of thepresent invention.

FIG. 32 is a schematic block diagram illustrating a crowbar module asbriefly described above regarding FIG. 31 , according to someembodiments of the present invention.

FIG. 33 is a top perspective view of a crowbar system according to someembodiments of the present invention.

FIG. 34 is a top perspective view of a crowbar module forming a part ofthe crowbar system of FIG. 33 .

FIG. 35 is a fragmentary, exploded, top perspective view of the crowbarmodule of FIG. 33 .

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which illustrativeembodiments of the invention are shown. In the drawings, the relativesizes of regions or features may be exaggerated for clarity. Thisinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein; rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the invention to thoseskilled in the art.

It will be understood that when an element is referred to as being“coupled” or “connected” to another element, it can be directly coupledor connected to the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlycoupled” or “directly connected” to another element, there are nointervening elements present. Like numbers refer to like elementsthroughout.

In addition, spatially relative terms, such as “under”, “below”,“lower”, “over”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. For example, if the device inthe figures is turned over, elements described as “under” or “beneath”other elements or features would then be oriented “over” the otherelements or features. Thus, the exemplary term “under” can encompassboth an orientation of over and under. The device may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein interpreted accordingly.

Well-known functions or constructions may not be described in detail forbrevity and/or clarity.

As used herein the expression “and/or” includes any and all combinationsof one or more of the associated listed items.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

According to embodiments described herein, an arc flash and surgeprotection system may protect electrical distribution and controlequipment from arc flashes that may be generated inside an enclosure,such as an electrical switchgear cabinet. In the event of an arc in theabsence of protections provided herein, a short circuit corresponding tothe arc may cause the circuit breaker to trip and open the circuitwithin about 100 milliseconds. In the case of lower short circuitcurrent due to, for example, circuit impedance, an arc flash detectionsystem may trigger the circuit breaker to trip. However, during thisperiod, the short circuit current, which may be between about 10 kA toabout 100 kA, will damage internal equipment within the switchgearcabinet, and may present a serious safety hazard for personnel proximatethe switchgear cabinet.

As disclosed herein, the above effects may be eliminated by using acrowbar device that has a very fast response time (e.g., less than about5 milliseconds) and that may conduct the fault current to eliminate thearc until the circuit breaker trips and disconnects the switchgearcabinet from the power source.

The crowbar device may include two thyristors (one for each direction ofAC current) that when triggered may create a short that will conduct thecurrent and eliminate the arc flash. However, as provided herein,thyristors may be protected against damage from false triggers and/orovervoltages. False triggers may be protected against using circuitcomponents described herein and overvoltage protection may be providedusing surge protection devices that may be connected in parallel withthe overvoltage protection device. The use of the surge protectivedevice may protect the thyristors of the crowbar device from falsetrigger and other equipment in the installation.

In some embodiments, the crowbar device may protect the surge protectiondevice in the event that the surge protection device has failed. Forexample, typical failure mode of such devices may be a short circuitthat is interrupted by either an internal thermal disconnector and/or anexternal fuse/circuit breaker. In this manner, the crowbar device mayfurther protect the surge protection device in case of its failure andtherefore obviate a need for a thermal disconnector and/or a seriesfuse/circuit breaker.

Some embodiments provide that the crowbar device may be implemented inseveral different ways. A first example provides for a single operationin that the crowbar device is used only once and a replacement crowbardevice is provided to replace the used crowbar device. A second exampleincludes a crowbar device that can be used multiple times. In thisexample, the crowbar device may withstand the short circuit currentuntil the circuit breaker trips. As such, the crowbar device may berestored after the fault event and allow a possible reclosure of themain circuit breaker that will permit the installation to resume normaloperation (provided that the problem that caused the tripping of thecrowbar system has been solved).

To trigger the crowbar device, a separate electronic circuit may beused. This circuit may receive the trigger signal from the arc flashdetector circuit as an input and may trigger the crowbar device and/orthe main circuit breaker. In some embodiments, this circuit may alsoreceive voltage and current readings of the power lines and currentreadings of the surge protection devices as inputs. In this manner, theelectronic system may indicate the presence of a short circuit anywheredownstream of the crowbar device, if there is an prolonged overvoltagecondition and if the surge protective devices failed. In any of theabove conditions (or any other condition that is required and can bedetected by using these sensors or additional sensors) the electronicsystem may trigger the crowbar device and the main circuit breaker.

In addition, the electronic circuit may also provide an alarm signal toindicate the presence of and/or type of problem that caused the trippingof the crowbar device. Some embodiments provide that the crowbar devicemay be triggered responsive to one or more of the following conditionsand/or events:

-   -   Arc Flash inside the cabinet;    -   Failure of the surge protective device;    -   Prolonged overvoltage or overcurrent conditions;    -   Short circuit downstream the crowbar device;    -   Any other pattern of electrical disturbance in the system that        can be detected using the existing sensors or by installing        additional sensors for that reason; and    -   Remote manual trigger.

Reference is now made to FIG. 3 , which is a block diagram illustratingan arc flash, overvoltage, overcurrent and surge protection systemaccording to some embodiments of the present invention. Some embodimentsof the present invention may be applicable to the protection ofequipment corresponding to switchgear systems used in industrialinstallations including secondary distribution panels and/or a serviceentrance section of electrical generation facilities, including, forexample, wind turbine generators. However, such embodiments arenon-limiting. For example, arc flash and surge protection systemsdescribed herein may be applicable to many different types of systemsthat may be susceptible to overvoltage conditions, surge currents and/orarc flash faults. For example, medium and/or low voltage switchgear forcontrolling and distributing single or multiphase electrical power mayuse arc flash and surge protections systems as described herein. In someembodiments, a switchgear cabinet 60 may include an arc flash,overvoltage, over current and surge protection system 100 configuredtherein to protect the equipment 50, the switchgear cabinet 60 and othercomponents included thereon and/or personnel proximate the switchgearcabinet 60.

Brief reference is now made to FIG. 4 , which is a block diagramillustrating an arc flash, overvoltage, over current and surgeprotection system according to some embodiments of the presentinvention. As illustrated, a three phase line may be connected to andsupply electrical energy to one or more transformers 66, which may inturn supply three phase electrical power to a main circuit breaker 68.The three phase electrical power may be provided to one or moredistribution panels 62. As illustrated, the three voltage lines of thethree phase electrical power may designated as L1, L2 and L3 and aneutral line may be designated as N. In some embodiments, the neutralline N may be conductively coupled to an earth ground.

Some embodiments include an arc flash, overvoltage, overcurrent andsurge protection system 100 connected between the phase lines L1, L2 andL3, and neutral (N). The arc flash, overvoltage, overcurrent and surgeprotection system 100 may protect other equipment in the installationsuch as the distribution panel 62 among others. In some embodiments, thearc flash, overvoltage, over current and surge protection system 100 maybe coupled to and/or receive one or more signals from an arc flashdetection system 64 that may be in a distribution panel 62 and/or otherequipment in the installation.

As discussed above, an arc flash, overvoltage, overcurrent and surgeprotection system 100 may implemented in a system corresponding to powerdistribution switchgear 60 that is configured to distribute multiphaseelectrical power. For example, reference is now made to FIG. 5 , whichis a schematic diagram representing a circuit including an arc flash andsurge protection system in a three phase switchgear cabinet according tosome embodiments of the present invention. As illustrated, a three phaseline may be connected to and supply electrical energy to one or moretransformers 66, which may in turn supply three phase electrical powerto a main circuit breaker 68 in the switchgear cabinet 60. Within theswitchgear cabinet 60, the three phase electrical power may be providedto one or more distribution panels 62 that may or may not be within theswitchgear cabinet 60. As illustrated, the three voltage lines of thethree phase electrical power may designated as L1, L2 and L3 and aneutral line may be designated as N. In some embodiments, the neutralline N may be conductively coupled to an earth ground.

In some embodiments, the arc flash, overvoltage, overcurrent and surgeprotection system 100 may include a crowbar device 102 that is operableto prevent an overvoltage condition by generating a low resistance pathfrom the three voltage lines L1, L2, L3 to the neutral line N. Althoughsome embodiments are discussed herein with reference to an overvoltagecondition, such embodiments may also refer to an overcurrent conditionthat may or may not be a result of an overvoltage condition. Someembodiments provide that the crowbar device may be triggered by atrigger circuit 106.

As illustrated, the crowbar device 102 may include an overvoltageprotection module 120 corresponding to each of the three phases L1, L2and L3. Each overvoltage protection module 120 may include twothyristors (e.g., TH5 and TH6) that are electrically coupled in parallelwith one another, but with opposite polarities. Stated differently, ananode of a first thyristor (e.g., TH5) of the pair of thyristors may becoupled to a cathode of the second thyristor (e.g., TH6) of the pair ofthyristors and a cathode of the first thyristor (TH5) of the pair ofthyristors may be coupled to the anode of the second thyristor (TH6) ofthe pair of thyristors. In this manner, when the thyristors aretriggered to be in a conductive state, each half of an alternatingcurrent waveform may be conducted from the phase to the neutral.

In some embodiments, an overvoltage protection module 120 may include acircuit of a resistor R and a capacitor C arranged in series with oneanother, such that the resistor-capacitor series RC is connected inparallel with the two thyristors (e.g., TH5 and TH6). Although describedand illustrated as a single resistor R and capacitor C, embodiments mayinclude more than one resistor and/or more than one capacitor to achievethe desired resistive and/or capacitive performance, but also to useextra R and C for redundancy, as the operation of this circuit may beimportant to prevent a false triggering of the thyristors. The snubbercircuit may slow down a rate of change in voltage (dV/dt) that mayotherwise result in falsely triggering the thyristor. For example, inthe absence of the RC snubber circuit, the thyristor may be triggered byelectrical noise that is unrelated to an actual overvoltage condition.The capacitor C may reduce the rate of change in voltage (dV/dt)together with the resistor R. The inductance L and the resistance R maylimit the inrush of current of the high capacitance value of thecapacitor C when the circuit is energized.

Some embodiments provide that an inductor L in arranged in series withthe pair of antiparallel-connected thyristors. The inductor L may limita rate of change in current (di/dt) through the thyristors, which mightotherwise damage the thyristors. Also, L, combined with the RC snubbercircuit, reduces the rate of change in voltage (dV/dt) at the thyristorsin case of an overvoltage generated in the power system. In this manner,a self-trigger of thyristors may be prevented.

Some embodiments provide that in a three-phase power system, a crowbardevice 102 includes three overvoltage protection modules 120 that may becoupled from respective phase conductors L1, L2 and L3 to a neutral N.In some embodiments, each of the overvoltage protection modules 120 is amodular component include all of the functional components therein in asingle assembly. Some embodiments provide that multiple (e.g., three ina three-phase power system) overvoltage protection modules 120 may beconfigured as a single assembly including the components andfunctionality for overvoltage protection for all phases in a singleassembly.

Some embodiments include surge protection devices (SPDs) 104. Asillustrated, each of the SPDs 104 may be connected between respectiveones of L1, L2 and L3, and neutral (N). The use of the SPD may protectthe thyristors of the crowbar device during lightning events and/ortransient overvoltage conditions, as well as protect other equipment inthe installation. In addition, the SPDs may be used to protect allequipment in case of prolong overvoltages. However, such a condition mayforce the SPD to conduct a limited current for a prolonged period oftime, which may result in the overheating of the SPD and possibly itsfailure (depending on the energy withstand capabilities the SPD canabsorb and the level and duration of the overvoltage condition). Suchevent may be addressed by tripping the crowbar device. A typicaloperating voltage of an SPD 104 in the present example may be about 400V(for 690V L-L systems). In this regard, the SPDs 104 will each performas an insulator and thus not conduct current during normal operatingconditions. In some embodiments, the operating voltage of the SPD's 104is sufficiently higher than the normal line-to-neutral voltage to ensurethat the SPD 104 will continue to perform as an insulator even in casesin which the system voltage increases due to overvoltage conditions thatmight arise as a result of a loss of power or other power system issues.

In the event of a surge current in, for example, L1, protection of powersystem load devices may necessitate providing a current path to groundfor the excess current of the surge current. The surge current maygenerate a transient overvoltage between L1 and N. Since the transientovervoltage significantly exceeds the operating voltage of SPD 104, theSPD 104 will become conductive, allowing the excess current to flow fromL1 through SPD 104 to the neutral N.

Once the surge current has been conducted to N, the overvoltagecondition ends and the SPD 104 becomes non-conducting again. However, insome cases, one or more SPD's 104 may begin to allow a leakage currentto be conducted even at voltages that are lower than the operatingvoltage of the SPD's 104. Under such conditions, the leakage current maybe measured using, for example, current transformers 105 that mayprovide leakage current values to the trigger circuit 106.

An arc flash detection system 64 may be configured to detect an arcflash within the switchgear cabinet 60 using one or more sensors and/orsensor types including photosensors, pressure sensors and/or currenttransformers, among others. The arc flash detection system may providean arc flash detection signal (AFD) to the trigger circuit 106.

The trigger circuit 106 may receive inputs corresponding the linevoltages L1, L2, L3, the line currents I1, I2, I3, the SPD leakagecurrents Is1, Is2, Is3, and the arc flash detection signal AFD. Asdescribed in more detail below, the trigger circuit 106 may, in responseto a fault circumstance, cause the crowbar device 102 to turn on, thusproviding a low resistance current path from the lines L1, L2, L3 to theneutral N, cause the main circuit breaker 68 to trip, and/or cause theSPD's to begin conducting. In some embodiments, the trigger circuit 106may further generate and/or transmit an alarm signal to one or moreother types of monitoring, logging or alarm equipment.

Some embodiments provide that the trigger circuit 106 is powered througha trigger circuit power supply 65, such as a single phase alternatingcurrent power source and/or a direct current power source. Someembodiments provide that the trigger circuit power supply 65 may becoupled to the trigger circuit 106 via one or more circuit interruptersor circuit breakers 67 and may be thus protected by the SPDs 104.

Reference is now made to FIG. 6 , which is a schematic block diagramillustrating a trigger circuit as briefly described above regarding FIG.5 , according to some embodiments of the present invention. In someembodiments, a trigger circuit 106 may include a power supply andvoltage hold-up circuit 166, which may receive single phase alternatingcurrent electrical power and/or direct current electrical power to powerthe trigger circuit. The power supply and voltage hold-up circuit 166may include a voltage hold-up circuit that may provide power to thetrigger circuit for at least 100 milliseconds after a condition whicheliminates the availability of the electrical power received from the atrigger circuit power supply 65.

In this manner, even with a loss of trigger circuit power due to a faultin another portion of the circuit, the power supply and voltage hold-upcircuit 166 maintains sufficient voltage for the trigger circuit 106 tofunction until the circuit breaker is capable of tripping. For example,during this period, trigger signals to all of the thyristors may bemaintained continually to keep the thyristors in a conducting state.Thus, the thyristors may be maintained in a conducting state until themain circuit breaker 68 has tripped. In the alternative, if a triggersignal to the thyristors is lost, the thyristors will only allow verylimited current flow therethrough, which may result in the arc flashrestarting.

Brief reference is now made to FIG. 7 , which is a schematic blockdiagram illustrating a power supply and voltage hold-up circuit 166 asdiscussed in reference to FIG. 6 above. In some embodiments, the powersupply and voltage hold-up circuit 166 is configured to receiveelectrical power as a single phase alternating current (AC) power sourceincluding a voltage line L_(p) and a neutral line N_(p). In suchembodiments, the received electrical power may be converted from AC todirect current (DC) using an AC-DC rectification unit 180. The resultingDC power may be smoothed using a smoothing capacitor 182.

The DC power may be provided to a voltage hold-up circuit 184 that mayinclude a holding resistor Rh that is connected in parallel with aholding diode Dh. The parallel combination of the holding resistor Rhand the holding diode Dh may be connected in series with a holdingcapacitor Ch. Some embodiments provide that the Rh, Dh, Ch circuit isconnected between the DC power line and the ground or neutral. In someembodiments, the anode of the holding diode Dh is connected to the DCpower line and the cathode of the holding diode Dh is connected to theholding capacitor Ch, the other terminal of which is connected to theground or neutral.

The power supply and voltage hold-up circuit 166 may include multipledifferent DC-DC isolated converters 186. For example, in the context ofa three phase system, a DC-DC isolated converter 186-1 may be providedto supply voltage (Vs, S) to a common driver in each of the threedifferent thyristor trigger circuits 168-1, 2, 3. Additionally, threeDC-DC isolated converters 186-2, 3, 4 may be provided to supply voltage(Vs1, S1; Vs2, S2; Vs3, S3) to respective ones of the thyristor triggercircuits 168-1, 2, 3, respectively.

Brief reference is now made to FIG. 8 , which is a block diagramillustrating a DC-DC isolated converter as discussed in reference toFIG. 7 above. A DC-DC isolated converter 186 may receive an input DCvoltage Vin to an inverter 191, which is configured to convert the DCinput voltage to an AC voltage. The AC voltage may be provided to anisolation transformer 192, which may produce a corresponding AC outputthat is conductively isolated from the input AC voltage that is receivedfrom the inverter 191. In some embodiments, the isolation transformer192 may include a coil winding ratio that is 1:1 such that the AC outputvoltage is at a same voltage level as the AC input voltage received bythe isolation transformer. Some embodiments provide that the isolationtransformer 192 coil winding ratio is not 1.0 and thus the AC outputvoltage may have a different voltage level from the AC input voltagereceived by the isolation transformer 192. The AC output voltage fromthe isolation transformer 192 may be received by a rectifier 193, whichis configured to convert the AC voltage to a DC output voltage.

Referring back to FIG. 6 , in some embodiments, the trigger circuit 106may include an interface circuit 164 that is configured to receiveinputs from various sensors and provide the data corresponding to thereceived inputs to a microcontroller 162. For example, the interfacecircuit 164 may receive inputs corresponding to: the voltages of thephase power lines L1, L2, L3 and the neutral N; an arc flash alarmsignal AFD from the arc flash detection system 64; current flow on thephase power lines I1, I2, I3; current flow through the SPD's Is1, Is2,Is3; and/or temperature of the SPDs Ts1, Ts2, Ts3, among others.

Some embodiments provide that the microcontroller 162 may process thereceived inputs and generate trigger signals to one or more thyristortriggers 168-1, 2, 3 to trigger the thyristors to a conduction mode. Insome embodiments, the microcontroller may further generate a trip signalTCB to the main circuit breaker 68. Some embodiments provide that themicrocontroller generates an alarm signal that may be provided to localand/or remote locations that may be monitored and/or that may includesupervisory control and data acquisition (SCADA). In some embodiments,the alarm signal is provided to a remote visual and/or audibleannunciator.

The microcontroller 162 may trigger the thyristors based on a variety ofcauses and/or events. For example, an arc flash may trigger an arc flashsignal to be sent to the microcontroller 162 from the arc flashdetection system 64. A system overvoltage condition corresponding one ormore lines having a voltage that exceeds a predetermined threshold for apredetermined period of time may cause the microcontroller to triggerthe thyristors. An overcurrent condition on one or more lines in whichthe current exceeds a predetermined current threshold for apredetermined period of time may cause the microcontroller to triggerthe thyristors.

In some embodiments, overheating of the surge protection devices 104 inwhich a temperature of the SPDs exceeds a predetermined temperaturethreshold for a predetermined period of time may cause themicrocontroller to trigger the thyristors. Additionally a short circuitmay be detected when a voltage drop of any phase line and acorresponding current increase of that phase line may cause themicrocontroller to trigger the thyristors.

Some embodiments provide that a detected end of life of an SPD may causethe microcontroller to trigger the thyristors. In some embodiments, suchan SPD may include a metal oxide varistor (MOV) and/or combined MOV/GDT(gas discharge tube). Such a condition may be determined by a voltagedrop in a phase line and a current rise in the corresponding SPD.

In some embodiments, the microcontroller may be configured to triggerthe overvoltage protection device only when specific combinations ofconditions and/or events are occurring with or without any constraintson the time interval between the conditions and/or events.

In some embodiments the thyristor triggers 168-1, 2, 3 may receive atrigger signal from the microcontroller 162 and provide control signalsto corresponding thyristor pairs to cause the respective thyristors toswitch from a substantially non-conducting state to a conducting state.For example, brief reference is now made to FIG. 9 , which is aschematic block diagram illustrating a thyristor trigger circuit 168-1as discussed above in reference to FIG. 6 .

Each of the thyristor trigger circuits 168 may be the same and may beoperable to trigger a pair of thyristors that correspond to a specificphase line. As such, FIG. 9 is directed to one of the thyristor circuitsof FIG. 6 , namely 168-1, which corresponds to the thyristors connectedto phase line L1. The common driver 172 may be powered by voltage linesVs and S that are provided from the power supply and voltage hold-upcircuit 166 and that are provided to the common driver 172 of each ofthe other thyristor trigger circuits 168-2, 3. The common driver 172changes state to provide a thyristor trigger signal TH1 responsive totrigger signal T1 from the microcontroller 162. Thyristor 1 changes to aconducting state responsive to the state change of TH1 and remains in aconducting state as long as TH1 is activated. In the case of thyristor1, the reference point C1 is the neutral line N.

The opto driver 170 may be powered by voltage lines Vs1 and S1 that areprovided from the power supply and voltage hold-up circuit 166. Incontrast with the DC voltage circuit Vs and S, the voltage lines Vs1 andS1 are not provided to other ones of the thyristor circuits 168-2, 3.The opto driver 170 changes state to provide a thyristor trigger signalTH2 responsive to trigger signal T2 from the microcontroller 162.Thyristor 2 changes to a conducting state responsive to the state changeof TH2 and remains in a conducting state as long as TH2 is activated. Inthe case of thyristor 2, the reference point C2 is the phase line L1.The phase voltage reference point is a reason for using an opto driverto isolate the output.

Referring back to FIG. 6 , the trigger circuit triggers all 6 of thethyristors at the same time and maintains the triggered state for atleast 100 milliseconds while at the same time the power is supplied tothe trigger circuit via the power supply and voltage hold-up circuit166. Additionally, while the thyristors are being triggered, the triggercircuit may provide a trigger signal to the main circuit breaker 68 andan alarm indicating the fault. In some embodiments, the alarm may alsoinclude data corresponding to a cause of the fault event.

Brief reference is now made to FIG. 10 , which is a schematic diagramrepresenting a circuit including an arc flash, overvoltage, overcurrentand surge protection system in a three phase switchgear cabinetaccording to some other embodiments of the present invention. Asillustrated, embodiments according to FIG. 10 differ from thosedescribed above regarding FIG. 5 in that the crowbar device 102 includesa bidirectional thyristor for each phase to neutral instead of twounidirectional thyristors in a complementary arrangement for each phase.Some embodiments provide that the bidirectional thyristors each rely onfour control wires for providing a trigger signal thereto. Otherfeatures of FIG. 10 are substantially similar to those discussed aboveregarding FIG. 5 and thus will not be repeated.

Reference is now made to FIG. 11 , which is a schematic diagramrepresenting a circuit including an arc flash, overvoltage, overcurrentand surge protection system in a three phase switchgear cabinetaccording to some other embodiments of the present invention. Asillustrated, embodiments according to FIG. 11 differ from thosedescribed above regarding FIG. 5 in that the crowbar device 102 includesthe thyristors and the SPDs 104. In some embodiments, ones of the SPDs104 are connected in the crowbar device 102 in parallel with thethyristor, RC and/or RLC circuits that are connected from each phase tothe neutral. Some embodiments provide that the SPDs 104 are metal oxidevaristors (MOVs) and/or combined MOV/GDT. In some embodiments, the MOVsmay be thermally fused to prevent overheating of the MOV in the case ofincreased leakage currents, which may be a typical occurrence when anovervoltage condition exists in the power system. In this regard, thetrigger circuit 106 may monitor the temperature rise and/or the thermalfuse and/or current through the MOV to indicate if the MOV has failed toshort. Responsive to such conditions, the thyristors may be quicklytriggered to prevent further damage of the whole device. Someembodiments provide that the thermal fuse may be sufficient to interruptleakage currents when the MOV has not failed to short, to preventoverheating of the device. Other features of FIG. 10 are substantiallysimilar to those discussed above regarding FIG. 5 and thus will not berepeated. To further reduce the overvoltage that could be applied to thethyristors, additional MOVs could be used in parallel to the snubbercircuit (RC).

Reference is now made to FIG. 12 , which is a schematic diagramrepresenting a circuit including an arc flash, overvoltage, overcurrentand surge protection system in a three phase switchgear cabinetaccording to some other embodiments of the present invention. Asillustrated, embodiments according to FIG. 12 differ from thosedescribed above regarding FIG. 5 in that the crowbar device 102 isconfigured to be connected from phase to phase instead of phase toneutral. Specifically, a thyristor and an RLC circuit is connected fromeach phase to another phase such that the crowbar device 102 may operatewithout conducting excess current to a neutral line N. Additionally, theSPDs 104 are connected from phase to phase to provide overvoltageprotection for one phase relative to the other phases. In someembodiments, the crowbar device 100 include a single thyristor that maybe a single directional thyristor. Other features of FIG. 10 aresubstantially similar to those discussed above regarding FIG. 5 and thuswill not be repeated.

As used herein, “monolithic” means an object that is a single, unitarypiece formed or composed of a material without joints or seams.

With reference to FIGS. 13-23 , a crowbar system 200 and a connectormodule 290 according to embodiments of the invention are shown therein.The crowbar system 200 corresponds to and is an implementation of thecrowbar system 102 of FIG. 5 . The connector module 290 corresponds toand is an implementation of a connector that may be connected betweenthe crowbar system 102 and the trigger circuit 106 as illustrated inFIG. 3 .

With reference to FIG. 13 , the system 200 includes three lineconductors L1B, L2B, and L3B (electrically connected to the lines L1, L2and L3, respectively, of FIG. 5 ), a neutral conductor NB (electricallyconnected to the neutral line N of FIG. 5 ), and three crowbar modules210(1), 210(2), and 210(3) according to embodiments of the invention andeach corresponding to a respective one of the modules 120 of FIG. 3 .The conductors L1B, L2B, L3B, NB may be substantially rigid, metalplates or busbars, for example. The conductors L1B, L2B, L3B, NB may bemounted in an electrical switchgear cabinet 60, for example. The crowbarmodules 210(1), 210(2), and 210(3) are electrically connected to theconnector module 290. Each of the crowbar modules 210(1), 210(2), and210(3) electrically and mechanically connects the neutral conductor NBwith a respective one of the line conductors L1B, L2B, L3B.

In some embodiments, the conductors L1B, L2B, L3B, NB are rigid busbarsand are rigidly affixed to and connected by the modules 210(1), 210(2),210(3) to collectively form a substantially rigid, unitary assembly ordevice 203 (FIG. 13 ).

With reference to FIGS. 14-21 , the crowbar module 210(3) is showntherein. The crowbar modules 210(1), 210(2), and 210(3) may besubstantially identical in construction and therefore only the crowbarmodule 210(3) will be described in detail below, it being understoodthat this description likewise applies to the other crowbar modules210(1), 210(2). Herein, the numeral 210 is used to describe each of thethree crowbar modules 210(1), 210(2), 210(3) generally.

The module 210(3) includes a plastic cover 212, a metal base busbar 214,fasteners 215, a coil assembly 220, an internal circuit board assembly230, a signal cable 232, and two thyristor assemblies or units 201, 202.

Each of the thyristor units 201 and 202 includes a thyristor 270. Thethyristor 270 of the unit 201 corresponds to the thyristor TH6 of FIG. 5and the thyristor 270 of the unit 202 corresponds to the thyristor TH5.

A center through hole 214B and outer through holes 214A are defined inthe busbar 214 (FIG. 16 ). The holes 214A may be countersunk or recessedto fully receive the heads of bolts 217. According to some embodiments,the busbar 214 is formed of aluminum. According to some embodiments, thebusbar 214 is unitary and, in some embodiments, monolithic.

The cover 212 and the busbar 214 form a module housing that defines anenclosed cavity 212A within which the coil assembly 220, the internalcircuit board assembly 230, the signal cable 232, and the crowbar units201, 202 are contained. The signal cable 232 extends out of the cover212 through a hole 212B and to the connection module 290.

The cover 212 may be formed of a dielectric or electrically insulatingmaterial having high melting and combustion temperatures. In someembodiments, the cover 212 is formed of a material that provides goodmoisture resistance. In some embodiments, the cover 212 is formed of apolymeric material and, in some embodiments, a silicone compound orpolybutylene terephthalate (PBT).

A filler material 218 (FIG. 14 ) fills the volume within the cavity notoccupied by the components 220, 230, 232, 201, 202. The filler material218 may be a dielectric or electrically insulating material having highmelting and combustion temperatures. In some embodiments, the fillermaterial is formed of a polymeric material and, in some embodiments,includes a material selected from the group consisting of epoxy castresin.

The coil assembly 220 (FIGS. 14 and 16-18 ) includes an electricallyconductive coil member 222, an electrically conductive busbar 224, anelectrically conductive terminal member 226, an electrical insulatorsheet 227, an electrically insulating casing 228, coupling screws 229Aand coupling bolts 229B.

The coil member 220 corresponds to the coil L (FIG. 5 ). The coil member220 includes a coil body 222A, a spirally extending coil strip 222Cdefining a spiral coil channel 222B, and a coupling extension 222D.Threaded bores 222E extend axially through the extension 222D andthrough holes 222F extend axially through the body 222A.

According to some embodiments, the coil member 220 is formed of metaland, in some embodiments, is formed of aluminum. According to someembodiments, the coil member 220 is unitary and, in some embodiments,monolithic.

The terminal member 226 includes a body 226A, a coupling extension 226B,and a terminal post 226C. Holes 226E extend axially through theextension 226B. A threaded bore 226D extends axially into the post 226C.The terminal member 226 is electrically and mechanically connected tothe coil member 220 by the bolts 229B, which extend through the bores222E, 226E. The insulator sheet 227 is interposed between the body 226Aand the body 222A to prevent or inhibit direct flow of electricalcurrent therebetween.

According to some embodiments, the terminal member 226 is formed ofmetal and, in some embodiments, is formed of aluminum. According to someembodiments, the terminal member 226 is unitary and, in someembodiments, monolithic.

The busbar 224 includes a body 224A that is substantially planar on itsupper side and has standoffs 224B projecting from its lower side. Boltholes 224C extend axially through the body 224A and the standoffs 224B.Fasteners 229A extend through holes 224D and into the coil body 222A tosecure the upper face of the busbar 224 in mechanical and electricalcontact with the coil body 222A.

According to some embodiments, the busbar 224 is formed of metal and, insome embodiments, is formed of aluminum. According to some embodiments,the busbar 224 is unitary and, in some embodiments, monolithic.

The casing 228 includes an outer shell portion 228A and a separator wallportion 228B. The outer shell portion 228A partially surrounds andencases the components 222, 224, 226, 227. Bolt holes 228C are definedin the portion 228A in alignment with the holes 222F. The terminal post226C projects through a post hole 228D and above the casing 228. Theseparator wall portion 228B fills the coil channel 222B between theadjacent windings of the coil strip 222C.

The casing 228 may be formed of a dielectric or electrically insulatingmaterial having high melting and combustion temperatures. In someembodiments, the casing 228 is formed of a polymeric material. In someembodiments, the casing 228 includes an epoxy. In some embodiments, thecasing 228 includes a material selected from the group consisting ofepoxy adhesive and/or epoxy cast resin or silicone elastomer. In someembodiments, the casing 228 is monolithic. In some embodiments, thecasing 228 includes a material selected from the group consisting ofepoxy adhesive and/or epoxy cast resin that is itself covered by anouter layer of a different material.

The outer casing layer 223 may be formed of a different material thatthe casing 228 in order to provide complementary properties. In someembodiments, the outer casing layer 223 is formed of a material thatprovides enhanced moisture resistance as compared to the material of thecasing 228. In some embodiments, the outer casing layer 223 is formed ofa silicone compound or PBT. The O-rings 223A (made of the same orsimilar material as the O-rings 265A, 265B) prevent leakage of the epoxyused in liquid form (initially) to form the casing 228.

The circuit board assembly 230 includes a substrate 230A (e.g., a PCB)and a capacitor 230B, a pair of resistors 230C, 230D, a lead wire 230E,and a lead bracket 230F mounted thereon. The capacitor 230B correspondsto the capacitor C (FIG. 5 ). The resistors 230C, 230D correspond to theresistor(s) R (FIG. 5 ). The capacitor 230B is electrically connected tothe busbar 224 by the wire 230E and the resistors 230C, 230D iselectrically connected to the busbar 214 by the lead bracket 230F. Theresistors 230C, 230D and the capacitor from a snubber circuit asdiscussed in more detail below.

With reference to FIGS. 16 and 19-21 , the crowbar unit 201 is showntherein. The crowbar units 201, 202 may be substantially identical inconstruction and therefore only the crowbar unit 201 will be describedin detail below, it being understood that this description likewiseapplies to the crowbar unit 202.

The crowbar unit 201 has a lengthwise axis A-A (FIG. 20 ). The crowbarunit 201 includes a first electrode or housing 240, a piston-shapedsecond electrode 250, a thyristor 270 between the housing 240 and theelectrode 250, and other components as discussed in more detail below.

With reference to FIGS. 19 and 20 , the housing 240 has an end electrodewall 242 and a cylindrical sidewall 244 extending from the electrodewall 242. The sidewall 244 and the electrode wall 242 form a chamber orcavity 241 communicating with an opening 246. A threaded bore 249extends axially into the electrode wall 242. A wire aperture or port 248extends through the side wall 244 and has an enlarged recess 248A at itsouter opening.

The electrode 250 has a head 252 disposed in the cavity 241 and anintegral shaft 254 that projects outwardly through the opening 246. Thethyristor 270 is disposed in the cavity 241 between and in contact witheach of the electrode wall 242 and the head 252.

Turning to the construction of the crowbar unit 201 in greater detail,the crowbar unit 201 further includes spring washers 262, flat washers264, an insulating member 266, an end cap 268, a retention clip 267,O-rings 265A, 265B, and a cable gland 280.

The electrode wall 242 of the housing 240 has an inwardly facing,substantially planar contact surface 242A. A locator feature or post 247projects upwardly from the contact surface 242A. An annular slot 243 isformed in the inner surface of the sidewall 244. According to someembodiments, the housing 240 is formed of aluminum. However, anysuitable electrically conductive metal may be used. According to someembodiments, the housing 240 is unitary and, in some embodiments,monolithic. The housing 240 as illustrated is cylindrically shaped, butmay be shaped differently.

As best seen in FIG. 20 , the head 252 of the electrode 250 has asubstantially planar contact surface 252A that faces the contact surface242A of the electrode wall 242. A threaded bore 255 is formed in the endof the shaft 254 to receive the bolt 215 for securing the busbar L3B tothe electrode 250. An annular, sidewardly opening groove 254D is definedin the shaft 254.

According to some embodiments, the electrode 250 is formed of aluminumand, in some embodiments, the housing sidewall 244 and the electrode 250are both formed of aluminum. However, any suitable electricallyconductive metal may be used. According to some embodiments, theelectrode 250 is unitary and, in some embodiments, monolithic.

An annular gap G1 is defined radially between the head 252 and thenearest adjacent surface of the sidewall 244. According to someembodiments, the gap G1 has a radial width in the range of from about 5to 15 mm.

The housing 240, the insulating member 266 and the end cap 268collectively define an enclosed chamber 245 containing the thyristor270.

The thyristor 270 includes a body 272 and an anode 274 and a cathode 276on axially opposed ends of the body 272. It will be appreciated that inFIG. 14 the internal structure and components of the thyristors are notshown in detail. The anode 274 and cathode 276 have substantially planarcontact surfaces 274A and 276A, respectively. The thyristor 270 isinterposed between the contact surfaces 242A and 252A such that thecontact surface 274A mates with the contact surface 242A and the contactsurface 276A mates with the contact surface 252A. As described below,the head 252 and the wall 242 are mechanically loaded against thethyristor 270 to ensure firm and uniform engagement between the matingcontact surfaces. The locator post 247 of the housing 240 is seated in acomplementary locator socket 277 formed in the contact surface 276A.

The thyristor 270 further includes a gate or control terminal 278A and areference terminal 278B. For example, as illustrated in FIG. 5 , aninput to the gate or control terminal 278A of the thyristor labeledtherein as TH5 may correspond to signal TH5 from the trigger circuit106. Similarly, a reference connection to a reference terminal 278B ofthe thyristor TH5 may correspond to the reference C5 from the triggercircuit 106.

With reference to FIG. 20 , the cable gland 280 is affixed in the wireport 248 and two signal wires 232A, 232B extend through the wire port248 and the cable gland 280 and into the chamber 245. The wire 232A iselectrically terminated at the control terminal 278A and the wire 232Bis electrically terminated at the reference terminal 278B.

The cable gland 280 includes a fitting 282 that is secured in the wireport 248. The fitting 282 has a cylindrical body 282A, a flange 282B anda through bore 282C. The body 282A is seated in the wire port 248 andthe flange 282B is seated in the recess 248A. The fitting 282 may besecured in place by adhesive 284, for example. In some embodiments, theadhesive 284 bonds the body 282A and the flange 282B directly to thewall of the wire port 248.

The cable gland 280 further includes a sealing plug 286 in the bore282C. The sealing plug 286 surrounds the wires 232A, 232B, bonds to thewires 232A, 232B and the fitting 282, and continuously fills the radialspace between the wires 232A, 232B and the fitting 282 and seals aboutthe wires 232A, 232B. In this manner, the sealing plug 286 serves tomechanically retain or secure the wires 232A, 232B in the port 282C(providing strain relief) and to fully seal, plug or close the bore 282C(e.g., hermetically).

The sealing plug 286 may be formed of a rigid material having highmelting and combustion temperatures. In some embodiments, the sealingplug 286 is formed of a polymeric material. In some embodiments, thesealing plug 286 is a hardened or cured resin. In some embodiments, thesealing plug 286 includes an epoxy. In some embodiments, the sealingplug 286 includes an epoxy adhesive or an epoxy cast resin.

The fitting 282 may be formed of a rigid material having high meltingand combustion temperatures. In some embodiments, the fitting 282 isformed of a polymeric material. In some embodiments, the fitting 282 isformed of Nylon-66 (PA-66), or equivalent.

A cable gland 280 can also be provided for sealing and penetration ofthe cable 232 through the cover 212 (FIG. 15 ).

The spring washers 262 surround the shaft 254. Each spring washer 262includes a hole that receives the shaft 254. The lowermost spring washer262 abuts the top face of the head 252. According to some embodiments,the clearance between the spring washer hole and the shaft 254 is in therange of from about 0.015 to 0.035 inch. The spring washers 262 may beformed of a resilient material. According to some embodiments and asillustrated, the spring washers 262 are Belleville washers formed ofspring steel. While two spring washers 262 are shown, more or fewer maybe used. The springs may be provided in a different stack arrangementsuch as in series, parallel, or series and parallel.

The flat metal washers 264 are interposed between the spring washer 262and the insulator ring 266 with the shaft 254 extending through holesformed in the washers 264. The washers 264 serve to distribute themechanical load of the upper spring washer 262 to prevent the springwasher 262 from cutting into the insulator ring 266.

The insulator ring 266 overlies and abuts the washer 264. The insulatorring 266 has a main body ring 266A and a cylindrical upper flange orcollar 266B extending upwardly from the main body ring 266A. A hole 266Creceives the shaft 254. According to some embodiments, the clearancebetween the hole 266C and the shaft 254 is in range of from about 0.025to 0.065 inch. An upwardly and outwardly opening peripheral groove 266Dis formed in the top corner of the main body ring 266A.

The insulator ring 266 is preferably formed of a dielectric orelectrically insulating material having high melting and combustiontemperatures. The insulator ring 266 may be formed of polycarbonate,ceramic or a high temperature polymer, for example.

The end cap 268 overlies and abuts the insulator ring 266. The end cap268 has a hole 268A that receives the shaft 254. According to someembodiments, the clearance between the hole 268A and the shaft 254 is inthe range of from about 0.1 to 0.2 inch. The end cap 268 may be formedof aluminum, for example.

The clip 267 is resilient and truncated ring shaped. The clip 267 ispartly received in the slot 243 and partly extends radially inwardlyfrom the inner wall of the housing 240 to limit outward axialdisplacement of the end cap 268. The clip 267 may be formed of springsteel.

The O-ring 265A is positioned in the groove 254 so that it is capturedbetween the shaft 254 and the insulator ring 266. The O-ring 265B ispositioned in the groove 266D such that it is captured between theinsulating member 266 and the sidewall 244. When installed, the O-rings265A, 265B are compressed so that they are biased against and form aseal between the adjacent interfacing surfaces. In an overvoltage event,byproducts such as hot gases and fragments from the thyristor 270 mayfill or scatter into the cavity chamber 245. These byproducts may beconstrained or prevented by the O-rings 265A, 265B from escaping thecrowbar unit 201 through the housing opening 246.

The O-rings 265A, 265B may be formed of the same or different materials.According to some embodiments, the O-rings 265A, 265B are formed of aresilient material, such as an elastomer. According to some embodiments,the O-rings 265A, 265B are formed of rubber. The O-rings 265A, 265B maybe formed of a fluorocarbon rubber such as VITON™ available from DuPont.Other rubbers such as butyl rubber may also be used. According to someembodiments, the rubber has a durometer of between about 60 and 100Shore A.

The electrode head 252 and the housing wall 242 are persistently biasedor loaded against the thyristor 270 along a load or clamping axis C-C(FIG. 20 ) to ensure firm and uniform engagement between the thyristorcontact surfaces 276A, 274A and the surfaces 242A, 252A. This aspect ofthe unit 201 may be appreciated by considering a method according to thepresent invention for assembling the unit 201, as described below.

The wires 232A, 232B are secured in the bore 282A of the fitting 282using the sealing plug 286. In some embodiments, the wires 278A, 278Bare inserted into the bore 282A, a liquid sealing material is introduced(e.g., poured or injected) into the bore about the wires 232A, 232B, andthe sealing material is cured to form the rigid sealing plug 286 on thewires 232A, 232B.

The fitting 282 is secured in the wire port 248 using the adhesive 284.The wires 232A, 232B are connected to the terminals 274A, 276A. In someembodiments, the wires 232A, 232B are secured by the sealing plug 286before the step of securing the fitting 282 in the wire port 248.

The O-rings 265A, 265B are installed in the grooves 254, 266D. Thethyristor 270 is placed in the cavity 241 such that the contact surface276A engages the contact surface 242A. The electrode 250 is insertedinto the cavity 241 such that the contact surface 252A engages thecontact surface 274A. The spring washers 262 are slid down the shaft254. The washers 264, the insulator ring 266, and the end cap 268 areslid down the shaft 254 and over the spring washers 262. A jig (notshown) or other suitable device is used to force the end cap 268 down,in turn deflecting the spring washers 262. While the end cap 268 isstill under the load of the jig, the clip 267 is compressed and insertedinto the slot 243. The clip 267 is then released and allowed to returnto its original diameter, whereupon it partly fills the slot and partlyextends radially inward into the cavity 241 from the slot 243. The clip267 and the slot 243 thereby serve to maintain the load on the end cap268 to partially deflect the spring washers 262. The loading of the endcap 268 onto the insulator ring 266 and from the insulator ring onto thespring washers 262 is in turn transferred to the head 252. In this way,the thyristor 270 is sandwiched (clamped) between the head 252 and theelectrode wall 242.

When the crowbar unit 201 is assembled, the housing 240, the electrode250, the insulating member 266, the end cap 268, the clip 267, theO-rings 265A, 265B and the cable gland 280 collectively form a unithousing or housing assembly 249 containing the thyristor 270.

The crowbar module 210 may be assembled as follows in accordance withmethods of the invention.

In order to construct the coil assembly 220, the busbar 224 is securedto the coil member 222 using the bolts 229A. The terminal member 226 issecured to the coil member 222 using the bolts 229B with the insulatorsheet 227 captured between the terminal member 226 and the coil member222. The casing 228 is thereafter molded about and through thissubassembly. For example, in some embodiments, the subassembly is placedin a mold, the mold is then filled with liquid casing material (e.g., aliquid resin), and the material is then cooled or cured to form therigid casing 228. The regions of the holes 228C, 228D, 222F, 226D may betemporarily filled or plugged with mold features or the like to preventthe liquid casing material from filling these regions. The casing 223 ismolding or fitted about the casing 228. For example, the casing 223 maybe molded or co-molded around the casing 228. Elastomeric O-rings 223Amay be fitted about the terminal post 226C and the busbar standoffs224B.

The coil assembly 220 is secured to the electrode 240 of the crowbarunit 201 by a bolt 217 and to the electrode 250 of the crowbar unit 202by a bolt 217. The heads of the bolts 217 are seated in the holes 228Cof the casing 228 to provide a low, flat profile. The base busbar 214 issecured to the electrode 250 of the crowbar unit 201 by a bolt 217 andto the electrode 240 of the crowbar unit 201 by a bolt 217. The heads ofthe bolts 217 are seated in the holes 214A of the base busbar 214 toprovide a low, flat profile. The lead wires 230E and 230F are secured tothe busbar 224 and the base busbar 214, respectively, by screws.

The cover 212 is installed over the foregoing subassembly and secured tothe base busbar 214 by fasteners (e.g., screws), adhesive, and/orinterlock features, for example. The cable 232 (which includes the wirepairs 232A, 232B from each of the crowbar units 201, 202) is routedthrough the opening 212B in the cover 212. The remaining volume of thecavity 212A is filled with the filler material 218. In some embodiments,a liquid filler material is introduced (e.g., poured or injected throughthe hole 214B) into the cavity 212A, and then cured to form the rigidfiller material 218.

The connection module 290 (FIGS. 13 and 22 ) includes a circuit orcircuits corresponding to an interconnection between the crowbar system102 and the trigger circuit 106. For example, some embodiments providethat the crowbar system 102 includes three crowbar modules 210(1),210(2) and 210(3) (schematically illustrated as crowbar module 120 inFIG. 5 ) that include connections to trigger circuit 106. Specifically,for example, each of cables 232 may correspond to a respective one ofthe crowbar modules 210 and may correspond to thyristor trigger signalsfor each of the two crowbar units 201 within each crowbar module 210 andreference signals for each of the two crowbar units within each crowbarmodule 210. The connection module 290 may include a surroundingenclosure 292, and multiple electrical contacts that are configured toprovide connections to contacts in a mating connector (not shown). Inthis manner, the crowbar system 102 may be connected to the triggercircuit 106.

In order to connect the crowbar modules 210(1), 210(2), 210(3) to theconductors L1B, L2B, L3B, NB, each of the line conductors L1B, L2B, L3Bis mechanically and electrically connected to the terminal member 226 ofa respective one of the crowbar modules 210(1), 210(2), 210(3) by a bolt215, and the neutral conductor NB is mechanically and electricallyconnected to the base busbars 214 of the crowbar modules 210(1), 210(2),210(3) by bolts 215.

In use, the crowbar system 200 and the crowbar modules 210(1), 210(2),210(3) perform as described above for the system 102 and the threemodules 120, respectively (FIG. 5 ).

When a triggering event occurs, and the thyristors 270 of a module 210conduct current between the lines the module 210 bridges (i.e., theneutral line N and the associated one of the lines L1, L2, L3). Asdiscussed above, the crowbar units 201, 202, and therefore thethyristors 270 thereof, are oriented in opposite directions in order toconduct current in respective ones of the AC current directions. In thecase of the crowbar unit 202 of the module 210, the current flowssequentially through the terminal post 226C, the terminal extension226B, the coil member extension 222D, the coil strip 222C, the coil body222A, the busbar 224, the electrode 250 mated to the busbar 224, thethyristor 270, the electrode 240 mated to the busbar 214, and the busbar214. In the case of the crowbar unit 201, the current flows sequentiallythrough the busbar 214, the electrode 250, the thyristor 270, theelectrode 240, the busbar 224, the coil body 222A, the coil strip 222C,the extension 222D, the extension 226B, and the terminal post 226C.

The construction and configuration of the crowbar modules 210 provides acompact, modular, unitarily packaged device that can be efficientlyintegrated into existing electrical equipment cabinets. The packagingprovides a simple and convenient arrangement and features for connectingthe modules 210 to the lines L1, L2, L3, N (e.g., via conductor busbarsL1B, L2B, L3B, NB).

Moreover, the construction and configuration of the crowbar modules 210can provide the crowbar modules 210 with increased strength anddurability to withstand the physical effect (electromagnetic forcesgenerated) of fault currents over a prolonged period of time, and otherelectrical and mechanical stresses in service. Therefore, it can safelywithstand the short circuit event (avoid any safety issues to thepersonnel and any damages ti the equipment of the installation as wellas the whole installation itself) when it is triggered.

The crowbar module 210 can operate when triggered in two distinct ways:one to withstand the fault current for the period of time required totrip the upstream main circuit breaker and a second (a different designthan the first) that the thyristors 270 cannot withstand the faultcurrent and fail in short. The second option is attractive due to thelower energy withstand capabilities of the thyristors employed in thedesign. However, in such case, the crowbar system 200 typically can onlybe triggered once, as after it is triggered, the system 200 is notrecoverable and it has to be replaced. In the case where the thyristors270 can withstand the fault current, two additional provisions aretypically required. One is that the inductance of the added coil 222 isused to eliminate the possibility of damaging the thyristors due to highdi/dt during the conduction of the fault currents (creates a hot spot onthe internal surface of the thyristor disk). The impedance of the coilis also useful to allow the snubber circuit 230B, 230C, 230D to preventthyristor self-trigger due to excessive dv/dt (reduce the dV/dt, thatrequires a certain impedance in the circuit—in some applications thiscould be part of the existing impedance of the system and allow theomission of the coil). The second is that even in this case there shouldbe provisions using the same construction for the crowbar module 210 towithstand the damage in case the thyristor fails short—typical failuremode of the thyristor. Therefore the configuration of the crowbar module210 is highly beneficial, and in some cases mandatory, for both designimplementations (withstand and failure of the crowbar module 210).

For example, when a module 210 is activated, a thyristor 270 thereof maybe damaged (e.g., as a result of carrying all of the fault current).However, the associated housing assembly 241 contains the damage (e.g.,debris, gases and immediate heat) within the crowbar unit 201, 202, sothat the module 210 fails safely. Moreover, the components of the module210 surrounding the unit 201, 202 can also contain any or buffer anyheat or damage products that escape the unit 201, 202. In this way, themodule 210 can prevent or reduce any damage to adjacent equipment (e.g.,switch gear equipment in the cabinet) and harm to personnel. In thismanner, the module 210 can enhance the safety of equipment andpersonnel. This can be a very important feature as the main reason forusing a crowbar system as discussed herein is the protection ofequipment and personnel from arc flash hazards that are typically causedby breaking the insulation between bus bars or by failures onsemiconductive devices (like thyristors, IGBTs, etc). So, such a systemmay be of limited or no significant value if it creates the samedamaging effects that it is employed to solve (hazardous failure ofsemiconductive devices).

The construction of the coil assembly 220, and in particular the casing228, provide a robust, unitary component. The enhanced strength of thecoil assembly 220 is beneficial to withstand the stresses that may beexperienced and exerted by the coil member 222, which is located inseries across lines.

The filler material 218 can provide the module 210 with improvedstrength. The filler material 218 can help to contain byproducts fromdestruction of the thyristor. The filler material 218 can thermalinsulate as well as electrically insulate electrical components of themodule 210 from the environment (e.g., personnel and other equipment inthe switch cabinet). The filler material 218 can also provide tamperresistance.

The cable gland 280 provides strain relief for the wires 232A, 232B, andalso serves to seal the wire port 248 to prevent or inhibit expulsion ofbyproducts from destruction of the thyristor through the wire port 248.

In some embodiments, the cable gland 280 is constructed to permit breachor failure of the cable gland 248 in response to pressure in the chamberexceeding a threshold pressure in a prescribed range. That is, the cablegland 280 can serve as a pressure dependent valve. This may be veryimportant feature in case for some reason the crowbar module 210 isoverexposed to fault currents—above its specifications—and the cablegland 280 operates as a pressure relief inside the module 210 withoutgenerating significant hazards (i.e., it is a controlled way to relievethe internal pressure by allowing a smoke emission in a specificdirection that could be externally controlled by guiding the smokeemissions to a vent.

A failure of the cable gland 280 can be observed without disassemblingthe crowbar unit 201, 202. The valve function the gland 280 can beadvantageously employed to determine the maximum fault current andduration that the crowbar module 210 can withstand, having as anindication only when the valve will open when the crowbar unit 201, 202is being tested or rated (used as a first indication that the faultcurrent withstand capability of the crowbar module 210 is close to itslimits, instead of experiencing a full damage of the whole module).

Electrical protection devices according to embodiments of the presentinvention (e.g., the device 210) may provide a number of advantages inaddition to those mentioned above. The devices may be formed so to havea relatively compact form factor. The devices may be retrofittable forinstallation in place of similar type crowbar devices not having athyristor as described herein. In particular, the present devices mayhave the same length dimension, as such previous devices. That dependson the fault current rating of the crowbar system, the duration of thefault current and the mode of operation during trigger (withstand orfailure). That determines the size of the thyristors 270 employed andtherefore the size and construction details of the crowbar modules 210and of the whole system.

According to some embodiments, the areas of engagement between each ofthe electrode contact surfaces (e.g., the contact surfaces 242A, 252A)and the thyristor contact surfaces (e.g., the contact surfaces 274A,276A) is at least one square inch.

According to some embodiments, the biased electrodes 240, 250 apply aload to the thyristor 270 along the axis C-C in the range of from 2000lbf and 26000 lbf depending on its surface area.

According to some embodiments, the combined thermal mass of the housing240 and the electrode 250 is substantially greater than the thermal massof the thyristor 270. As used herein, the term “thermal mass” means theproduct of the specific heat of the material or materials of the object(e.g., the thyristor 270) multiplied by the mass or masses of thematerial or materials of the object. That is, the thermal mass is thequantity of energy required to raise one gram of the material ormaterials of the object by one degree centigrade times the mass ormasses of the material or materials in the object. According to someembodiments, the thermal mass of at least one of the electrode head 252and the electrode wall 242 is substantially greater than the thermalmass of the thyristor 270. According to some embodiments, the thermalmass of at least one of the electrode head 252 and the electrode wall242 is at least two times the thermal mass of the thyristor 270, and,according to some embodiments, at least ten times as great. According tosome embodiments, the combined thermal masses of the head 252 and thewall 242 are substantially greater than the thermal mass of thethyristor 270, according to some embodiments at least two times thethermal mass of the thyristor 270 and, according to some embodiments, atleast ten times as great.

As discussed above, the spring washers 262 are Belleville washers.Belleville washers may be used to apply relatively high loading withoutrequiring substantial axial space. However, other types of biasing meansmay be used in addition to or in place of the Belleville washer orwashers. Suitable alternative biasing means include one or more coilsprings, wave washers or spiral washers.

According to further embodiments of the invention, the crowbar module210 may be constructed with only one crowbar unit 201 or 202 (i.e., theother crowbar unit 202 or 201 is omitted), so that the crowbar module soformed electrically conducts only in one direction. Such modifiedcrowbar modules may be used in matched, inverted pairs to provide thefunctionality of the crowbar module 210.

According to further embodiments of the invention, the crowbar module210 may be constructed with only one crowbar unit 201 or 202 (i.e., theother crowbar unit 202 or 201 is omitted), but such that the remainingsingle crowbar unit 201, 202 includes, in place of the thyristor 270, abi-directional thyristor that can operate in both directions. That is,when triggered, the bi-directional thyristor will conduct current inboth directions of the AC current. This crowbar module may be reduced insize and/or cost as compared to the dual thyristor crowbar module.

According to further embodiments of the invention, the crowbar module210 may be constructed without the coil 222.

With reference to FIG. 23 , a crowbar module 310 according to furtherembodiments of the invention is shown therein. The crowbar module 310corresponds to the crowbar module 210, except as described below. InFIG. 23 , the cover 212, the filler material 218, and the crowbar unit201 are not shown, in order to provide clearer view for the purpose ofexplanation. The crowbar unit 201 in the crowbar module 310 iselectrically connected to the base busbar 214 and the coil member 222 bythe bolts 217A and 217B as in the crowbar module 210.

The crowbar module 310 includes an integral metal-oxide varistor (MOV)device 288. The integrated MOV device 288 is electrically connected tothe terminal member 226 by a lead 289A (bypassing the coil 222C), and tothe base busbar 214 by a lead 289B. The MOV device 288 is mounted on anelectrically insulating substrate 288C between the leads 289A, 289B. TheMOV device 288 includes a first pin type lead electrically contactingthe lead 289A and a second pin type lead electrically contacting thelead 289B. The MOV internally includes a thermal link (thermaldisconnector or thermal fuse) between the lead 288A and the oneelectrode of the MOV. The other electrode of the MOV is connected tolead 288B. In addition, the connection between the 226 and the MOV lead288A, as well as the connection between the busbar 214 and the lead288B, is done using a bus bar to enable the connections to the powerline and the ground to withstand the forces generated form the conductedcurrent when the MOV conducts surge/lightning currents or fault currentsfrom the power source. The crowbar module 310 may be used as a crowbarmodule in the crowbar device 102 of the system described above withreference to FIG. 11 for example. An additional MOV could also beused—integrated in the PCB 288C—and connected in parallel to the twothyristors to reduce the overvoltage at their ends and to prevent themaximum expected overvoltage which could lead to the false trigger ofthe thyristor.

Reference is now made to FIG. 24 , which is a schematic diagramillustrating an arc flash, overvoltage, overcurrent and surge protectionsystem according to some embodiments of the present invention. FIG. 24may include elements that are described above regarding at least FIG. 5and thus additional description thereof may be omitted. In someembodiments, the arc flash, overvoltage, overcurrent and surgeprotection system 500 may protect the electrical system of a windturbine generator from arc flash, overcurrent and/or surge or lightningevents. Some embodiments provide that arc flash, overvoltage,overcurrent and surge protection system 500 includes a crowbar device502 that is operable to prevent an overvoltage condition by generating alow resistance path from the phase voltage lines L1, L2, L3 to theneutral line N. Some embodiments provide that the crowbar device 502includes crowbar modules 520 that are each connected between thecorresponding phase voltage line L1, L2, L3 and the neutral line N.

Some embodiments provide that each of the crowbar modules 520 maybeconnected to a current sensor 505 that may monitor the current flow ofthe corresponding phase line. In some embodiments, the current sensor505 may be separate from the crowbar module 520 and/or the crowbardevice 502 while in some other embodiments the current sensor 505 may beintegrated into the crowbar module 520 and/or the crowbar device 502.

Some embodiments include surge protection devices (SPDs) 104. Asillustrated, each of the SPDs 104 may be connected between respectiveones of L1, L2 and L3, and neutral (N). The use of the SPD 104 mayprotect the thyristors of the crowbar device 502 during lightning eventsand/or transient overvoltage conditions, as well as protect otherequipment in the installation.

In some embodiments, the crowbar device 502 may be triggered by an arcflash trigger circuit 506. As described above, an arc flash detectionsystem 64 may be configured to detect an arc flash within the switchgearcabinet 60 and provide an arc flash detection signal (AFD) to the arcflash trigger circuit 506. In some embodiments, the arc flash triggercircuit 506 may manage trigger and alarm signals from the crowbarmodules 520 and provide the trigger outputs to one or more circuitbreakers 68. Some embodiments provide that the arc flash trigger circuit506 may also provide indications corresponding to the condition of eachcrowbar module 520 and a cause of triggering ones of the crowbar modules520.

The arc flash, overvoltage, overcurrent and surge protection system 500may also include a threshold selector 510 that provides a signal to thearc flash trigger circuit 506 to set the current threshold at which thearc flash trigger circuit 506 causes the crowbar module 520 to actuate.

In use and function, under normal operating conditions, a crowbar module520 may remain inactive and thus not conduct current between phase linesL1, L2, L3 and the neutral line N. Normal operating conditions mayinclude those in which a phase line voltage is less than a specificthreshold. For example, in some embodiments, the specific threshold maybe about 1800 V peak, however, such embodiments are non-limiting as thethreshold voltage may be more or less than 1800 V.

A crowbar module 520 may be triggered in different ways depending onwhen a fault condition is detected. For example, the crowbar module 520may be triggered in a first manner during a start-up period and a secondmanner during steady state operation.

During a start-up period, such as within about 2 seconds or less fromthe start of a wind turbine or other generating device, the crowbarmodule 520 may operate without a power supply from the arc flash triggercircuit 506. In this regard, the crowbar module 520 cannot be triggeredby an alarm signal from the arc flash detection system 64 as such systemis generally unavailable for operation during a start-up period. In thismanner, the crowbar module 520 may be self triggered during the start-upperiod.

Reference is now made to FIG. 25 , which is a schematic block diagramillustrating a crowbar module as briefly described above regarding FIG.24 , according to some embodiments of the present invention. The crowbarmodule 520 may include two thyristors TH1, TH2 that are connectedanti-parallel to one another and in series with an inductor L. As usedherein, the term “anti-parallel” may refer to a configuration in whichcomponents are connected in parallel with one another, but in acomplementary arrangement relative to one another. For example, an anodeterminal of a first component may be connected to a cathode terminal ofa second component while the cathode terminal of the first component isconnected to the anode terminal of the second component. In someembodiments, a resistor R and a capacitor C may be connected in serieswith one another and in parallel with the thyristors TH1, TH2. Thecrowbar module 520 may further include the crowbar trigger circuit 530that is configured to provide a self triggering function within thecrowbar module 520. During a start-up period, the crowbar triggercircuit 530 may be powered by current received from the current sensor505. For example, the crowbar module 520 may be self triggered once thecurrent through the phase line is above the threshold current (I_(TH))for a period of more than 2 ms. In such cases only the crowbar module520 that is connected to the corresponding phase line may be triggered.

Brief reference is now made to FIG. 27 , which is a graph illustratingvoltage and current values during a fault condition according to someembodiments of the present invention. Continuing with the example above,at time t1 a fault current I reaches the threshold current I_(TH). Attime t2, responsive to the fault current I exceeding the thresholdcurrent I_(TH) for a specific period of time, crowbar module 520 beginsto conduct the fault current thus reducing the voltage for the remainingportion of that cycle at time t3 to about zero volts. If the fault isstill present during the second half of the cycle, then the crowbarmodule 520 again conducts the fault current thus reducing the voltagefor the remaining portion that cycle.

Referring back to FIG. 25 , some embodiments provide that every time thecrowbar module 520 is triggered a trigger signal will be provided to thearc flash trigger circuit 506. In some embodiments, the response time ofthe crowbar module 520, from the time the overcurrent is detected, maybe less than about 1 ms. In some embodiments, the response time may beless than about 500 μs. Some embodiments provide that the response timemay be about 300 μs

Reference is now made to FIG. 26 , which is a schematic block diagramillustrating a crowbar trigger circuit of the crowbar module as brieflydescribed above regarding FIG. 25 , according to some embodiments of thepresent invention. The crowbar trigger circuit 530 may receive a currentsignal from current sensor 505 into one or more step up transformers510, 512. Since the current signal and the output from the step uptransformers 510, 512 may be an alternating current (AC) signal, theoutputs from the step up transformers 510, 512 may be received byrectifiers 520, 522, respectively. The rectifiers 520, 522 may generatedirect current (DC) signals that correspond to the current signal fromthe current sensor 505.

The crowbar trigger circuit 530 may also include variable referencesignal generators 530, 532 which provide reference signals correspondingto the selected value of I_(TH). Comparators 540, 542 may be configuredto receive the DC signals from the rectifiers 520, 522, respectively andreference signals from the variable reference generators 532, 530.Responsive to the one of DC signals from the rectifier exceeding thereference signal, the output state of the comparator changes from highto low, or vice versa. The crowbar trigger circuit 530 may include delaycircuits 550, 552 that are configured to receive output signals from thecomparators 540, 542. Responsive to receiving a changed output from thecomparators 540, 542, the output of the delay circuits 550, 552 willchange after a given time delay. By providing the time delay, a falsetriggering of the thyristors may be prevented and/or reduced. The outputfrom the delay circuits 550, 552 may provide thyristor trigger signalsvia diodes 588, 582 that cause corresponding ones of the thyristors toturn on into a conducting state.

In some embodiments, the delay circuits 550, 552 may provide differentreference voltage signals relative to one another. For example, delaycircuit 550 may provide a positive voltage relative to the neutral linefor triggering thyristor TH1. Similarly, delay circuit 552 may provide apositive voltage relative to the inductor bottom terminal L_(TH).

While the above describes the self-triggering operation of the crowbartrigger circuit 530 during a start-up period, once the start-up periodis over the normal operation of the crowbar module 520 is responsive tothe arc flash trigger circuit 506. The crowbar trigger circuit 530 mayreceive a control voltage Vcc and ground into DC-DC converters 570, 572.In some embodiments, a first DC-DC converter 572 may provide a DCvoltage that is capable of triggering the first thyristor TH1 and asecond DC-DC converter 570 may provide a DC voltage that is capable oftriggering the second thyristor TH2. The crowbar trigger circuit 530 mayalso receive an arc flash detection signal into a driver 580. Inresponse, the driver 580 may energize optical switches 560 and 562,causing the DC voltages to be applied to the thyristors TH1, TH2 viadiodes 584, 588.

Reference is now made to FIG. 28 , which is a schematic block diagramillustrating an arc flash trigger circuit of the crowbar module asbriefly described above regarding FIG. 24 , according to someembodiments of the present invention. The arc flash trigger circuit 506may receive a ground and an operating voltage Vcc, such as, for example,24 V DC. A latch circuit 546 may receive and latch an alerted state ofan arc flash signal received from an arc flash detection system 64. Someembodiments provide that the arc flash trigger circuit 506 includes aplurality of output triggers 544 that may be used to provide a tripsignal to one or more circuit breakers and/or alarms.

In some embodiments, the arc flash trigger circuit 506 include a matrix548 that is configured to receive a discrete digital input from athreshold selector 510 and to generate a current threshold value basedon the value of the received digital input signal. Some embodimentsprovide that the threshold selector 510 may be a rotary switch thatprovides a discrete digital signal, such as a two bit binary signal. Insuch embodiments, different outputs of the threshold selector 510 may be00, 01, 10 and 11. In some embodiments, the 00 may correspond to adefault threshold current value that is used in the self-triggeringoperation of the crowbar module 520. In this manner, the absence of asignal during a start-up period may correspond to the 00 binary value.By way of example, current threshold values corresponding to thedifferent binary signals may include 6.3 kA, 500 A, 8 kA and 10 kA.

The arc flash trigger circuit 506 may provide a reliable voltage(V_(CC)) to the three crowbar modules 520 after the first 2 s from thestart-up and may transfer the alarm signal from the arc flash detectionsystem 64 to the three crowbar modules 520 without introducing any delayafter the first 2 s from the start-up.

In some example embodiments, the crowbar module 520 may be triggeredwhen the current through the power line is above I_(TH) peak for aperiod of more than 2 ms. In that case, only the crowbar module 520 thatis connected to the corresponding power line is self triggered each timethe current goes above I_(TH). In some embodiments, the response time ofthe crowbar module 520 once triggered is around 300 μs.

Some embodiments provide that the crowbar module 520 may also betriggered when there is an alarm signal from the arc flash detectionsystem 64. In that case, all three crowbar modules 520 are triggereduntil the main circuit breaker 68 is tripped. Some embodiments providethat the response time of the crowbar module 520 once triggered, is lessthan 2 ms, and may typically be around 300 μs. Then, the crowbar module520 will be in continuous trigger for a period of 100 ms.

Some embodiments provide that an arc flash and surge protection systemmay include a crowbar module as an electronic switch that is connectedin series with an energy absorber. In such applications, there TOV(overvoltages) in the system that could damage the equipment. In thisregard, a solution to direct part of the energy to a device that willabsorb it may be advantageous. Some embodiments include an energyabsorber that may be based on multiple metal oxide varistors (MOVs) thatare connected in parallel to absorb the TOV event. For example, thevoltage may be clamped during such an event by turning on the MOVs toconduct some current when the voltage is increased.

For example, for a 240V system, the peak voltage is 336V. The use of anMOV with a Maximum Continuous Operating Voltage (MCOV) of 250 VAC asclose as possible to the nominal voltage may be used such that duringnormal conditions the MOV will not conduct any current. The MOV mayconduct a very small leakage current (˜1 mA) at 336V. However, as thevoltage is increased, the MOV may start conducting heavily in an effortto limit the voltage. In this case, the voltage cannot exceed the valueof 1000V peak.

However, there are power systems that may need protection at much lowervoltage levels, for example 700V instead of 1000V. In such cases, toreduce the protection level, MOVs with lower MCOV, i.e. thinner MOVdisks, may be used. For example, the MOV may have a MCOV of 150 VACinstead of 250 VAC. In such cases, under normal operation the MOV mayconduct a significant current (above a few Amps) that will force it tofailure within a limited period of time (depending on the exact level ofthe conducted current). In this regard, an energy absorber may be usedwith an MOV having an MCOV of 150 VAC in series with one another.

For example, reference is now made to FIG. 29 , which is a schematicblock diagram illustrating a surge protection system used in protectingequipment according to some embodiments of the present invention. Asillustrated, the arc flash, overvoltage, overcurrent and surgeprotection system 600 may include a crowbar device 602 that is connectedbetween the different phase lines L1, L2, L3. The crowbar device 602 maybe connected in series with multiple MOVs 605 that are connected torespective ones of the plurality of phase lines L1, L2, L3.

The crowbar device 602 may function as a switch that will connect theMOVs 605 that function as energy absorbers to the phase lines only whenthe voltage exceeds a given threshold. In some embodiments, the giventhreshold is about 600V, however, this is merely a non-limiting example.The MOVs 605 may conduct as much current as necessary to keep thevoltage below 700 V. By way of example, based on the voltage-currentcurve of a 150 VAC MOV, at 700 V, the MOV 605 may conduct 10 kA ofcurrent, which exceeds the current that can be produced by the TOV. Assuch, the phase lines L1, L2, L3 cannot reach the 700V level.

Additionally, when the sinusoidal system voltage declines to cross thezero level, the impedance of the MOV will increase and will limit thecurrent through the thyristor in the crowbar module 602. Then when thecurrent through thyristor in the crowbar device 602 goes below 200 mA,the thyristor will disconnect the energy absorber from the system. Thismay occur as soon as the system voltage drops below 280V peakapproximately.

Brief reference is now made to FIG. 30 , which is a schematic blockdiagram illustrating a crowbar device as briefly described aboveregarding FIG. 29 , according to some embodiments of the presentinvention. The crowbar device 602 may include a plurality of thyristorsTH1, TH2, TH3 that are connected between the different pairs of theplurality of phase lines L1, L2, L3. A crowbar device trigger circuit630 may include a rectification circuit 632 that receives three phase ACcurrent from the plurality of phase lines L1, L2, L3 and generates acorresponding DC signal. The crowbar device trigger circuit 630 mayinclude a comparator 634 that receives the DC signal and a referencevoltage Vr and compares the two signals. If the DC signal exceeds thereference voltage Vr, then the comparator 634 generates an output to aplurality of trigger drivers 636 that are configured to trigger thethyristors into a conduction mode responsive thereto. Once the DC signaldrops below the reference voltage Vr, then the comparator 634 outputchanges state and the trigger drivers 636 turn off the thyristors.

Reference is now made to FIG. 31 , which is a schematic block diagramillustrating a surge protection system 60 used in protecting equipmentaccording to some embodiments of the present invention. Instead of theline to line connection described above regarding FIGS. 29 and 30 , thearc flash, overvoltage, overcurrent and surge protection system mayinclude a crowbar device 700 that includes MOVs 705 that are seriesconnected with crowbar modules 720 from each phase line L1, L2, L3 toneutral N. Since each phase line includes an independent MOV 705/crowbar720 module combination, then a fault at an individual phase line may beaddressed without triggering the MOV 705/crowbar module 720 combinationof the other phase lines. Brief reference is now made to FIG. 32 , whichis a schematic block diagram illustrating a crowbar module as brieflydescribed above regarding FIG. 31 , according to some embodiments of thepresent invention. A crowbar device trigger circuit 730 may include arectification circuit 732 that receives an AC phase current from acorresponding phase line and generates a corresponding DC signal. Thecrowbar device trigger circuit 730 may include a comparator 734 thatreceives the DC signal and a reference voltage Vr signal and comparesthe two received signals. If the DC signal exceeds the reference voltageVr, then the comparator 734 generates an output to a trigger driver 736that then activates an optical isolator 738. The output from the opticalisolator 738 is configured to trigger the thyristors TH1, TH2 into aconduction mode responsive thereto. Once the DC signal drops below thereference voltage Vr, then the comparator 734 output changes state andthe trigger driver 736 turns off the thyristors TH1, TH2.

With reference to FIGS. 33-35 , a crowbar system 800 according tofurther embodiments of the invention is shown therein. The crowbarsystem 800 includes a crowbar device 802 (corresponding to the crowbardevice 502 of FIG. 24 ), a trigger and alarm interface circuit unit 806(corresponding to the trigger circuit 506 of FIG. 24 ), and a remotethreshold selector switch 807 (corresponding to the threshold selector510 of FIG. 24 ).

With reference to FIG. 33 , the crowbar device 800 includes threecrowbar modules 810, three SPDs 804, a neutral conductor NB, lineconductors L1B, L2B, L3B, and three current sensors 805. The crowbardevice 800 further includes a crowbar device housing 860 (shown indashed lines) within which the crowbar modules 810, SPDs 804, conductorsNB, L1B, L2B, L3B, and current sensors 805 are mounted, disposed andencased.

In some embodiments, the trigger and alarm interface circuit unit 806and the remote selector switch 807 are located outside of the crowbardevice housing 860. For example, the trigger and alarm interface circuitunit 806 may be located elsewhere in an electrical service cabinetcontaining the crowbar device 802 and the lines L1, L2, L3 so that thetrigger and alarm interface circuit unit 806 is better positioned foroperator access or to detect activity in the cabinet. The remoteselector switch 807 may be located a substantial distance (e.g., atleast 20 feet) from the crowbar device 802. For example, the crowbardevice 802 may be located high above the ground on a tower while theremote selector switch 807 is mounted near ground level to enableconvenient access by an operator.

The crowbar modules 810 correspond to the crowbar modules 520 of FIG. 24. Each of the crowbar modules 810 is electrically and mechanicallycoupled to the neutral conductor NB (corresponding to neutral line N)and a respective one of the line conductors L1B, L2B, L3B (correspondingto the lines L1, L2, L3).

A respective SPD 804 (corresponding to the SPDs 104 of FIG. 24 ; e.g.,an MOV-based SPD) is mounted between and electrically connects theassociated line conductor L1B, L2B, L3B and the neutral conductor NB inparallel to the associated crowbar module 810.

The current sensors 805 correspond to the current sensors 505. Each ofthe current sensors 805 is operatively mounted on a respective one ofthe line conductors L1B, L2B, L3B and has an output signal wire 805Aconnected to the associated crowbar module 810.

Each crowbar module 810 is also electrically connected by an electricalcable 806A to the trigger and alarm interface circuit unit 806. Theremote selector switch 807 is in turn electrically connected to theinterface circuit unit 806 by an electrical cable 807A.

The crowbar modules 810 may be constructed and operate generally asdescribed herein with regard to the crowbar module 210, except asdescribed below. Each module 810 may include a filler materialcorresponding to the filler material 218; however, this filler materialis not shown in FIG. 35 .

With reference to FIGS. 34 and 35 , the crowbar module 810 includes amodule housing 811 defining an enclosed chamber 811A. The module housing811 includes an outer cover 812, a removable cover or back plate 813,and a base plate 815. The outer cover 812 is provided with a rear sideopening 812A. The opening 812A is closed and environmentally sealed by aremovable cover or back plate 813. The interface between the back plate813 and the cover 812 about the opening may be hermetically sealed by arubber seal 813A. In some embodiments, the chamber 811A is hermeticallysealed or moisture sealed.

With reference to FIG. 35 , crowbar units 801, 803 corresponding to thecrowbar units 201, 202 and a circuit board assembly 830 corresponding tothe circuit board assembly 230 are disposed in the chamber 811A betweena coil assembly 820 (corresponding to coil assembly 220) and a basebusbar 814.

The circuit board assembly 830 may include a snubber circuitcorresponding to the snubber circuit of the circuit board assembly 230.

An internal circuit board assembly 833 is secured to the back plate 813in the chamber 811A. The internal circuit board assembly 833 may includethe crowbar self trigger circuit 530 of the crowbar module 520 of FIGS.25 and 26 . Advantageously, placing the trigger circuit 530 in thecrowbar module housing 811 in close proximity to the thyristors TH1, TH2can reduce or prevent induced noise on the cables that might otherwisetrigger the thyristors TH1, TH2 accidentally.

An electrical connector 813B is mounted on the back plate 813 toelectrically connect the wires 805A, 806A to the circuit board assembly830, the circuit board assembly 833, and the thyristors of the crowbarunits 801, 803. The electrical connector 813B may be environmentallysealed.

Various inventive aspects as disclosed herein may be used independentlyof one another. For example, a crowbar unit 201 including a cable gland280 as described may be used without the unitarily assembling thecrowbar unit 201 with a coil, busbars, a snubber circuit, and or anothercrowbar unit.

Many alterations and modifications may be made by those having ordinaryskill in the art, given the benefit of present disclosure, withoutdeparting from the spirit and scope of the invention. Therefore, it mustbe understood that the illustrated embodiments have been set forth onlyfor the purposes of example, and that it should not be taken as limitingthe invention as defined by the following claims. The following claims,therefore, are to be read to include not only the combination ofelements which are literally set forth but all equivalent elements forperforming substantially the same function in substantially the same wayto obtain substantially the same result. The claims are thus to beunderstood to include what is specifically illustrated and describedabove, what is conceptually equivalent, and also what incorporates theessential idea of the invention.

1-21. (canceled)
 22. A surge protection system comprising: a crowbardevice that is coupled to and between a plurality of phase lines and isconfigured to prevent an overvoltage condition by selectively generatinga low resistance current path between the plurality of phase lines; anda plurality of surge protection devices that are connected to respectiveones of the plurality of phase lines and to the crowbar device and thatare configured to protect the equipment during an overvoltage conditionby conducting a limited amount of current that corresponds to theovervoltage condition.
 23. The surge protection system according toclaim 22, wherein ones of the plurality of surge protection devices eachcomprise: a first terminal that is connected to a corresponding one ofthe plurality of phase lines; and a second terminal that is connected tothe crowbar device, wherein the crowbar device comprises: a plurality ofphase terminals that are connected to the plurality of surge protectiondevices; and a plurality of thyristors that are connected betweendifferent pairs of the phase terminals.
 24. The surge protection systemaccording to claim 23, wherein the crowbar device further comprises acrowbar trigger circuit that is operable to generate thyristor triggersignals to the plurality of thyristors responsive to detecting a faultcondition on the phase lines.
 25. The surge protection system accordingto claim 24, wherein the crowbar trigger circuit comprises: arectification circuit that generates a direct current (DC) signalcorresponding to voltages between the plurality of phase lines; acomparator that compares the DC signal from the rectification circuit toa reference signal; and a plurality of isolation drivers that receive acomparator output, and, responsive to the comparator output indicatingthat the DC signal exceeds the reference signal, generates a triggersignal that turns on the plurality of thyristors.
 26. The surgeprotection system according to claim 22, wherein the surge protectiondevices comprise metal oxide varistors. 27-71. (canceled)
 72. A crowbarsystem comprising: a crowbar module including: a module housing; athyristor disposed in the module housing; a coil disposed in the modulehousing; a trigger circuit disposed in the module housing; and a snubbercircuit disposed in the module housing; and an external trigger andalarm interface circuit electrically connected to the crowbar module.73. The surge protection system of claim 23, further comprising: aplurality of snubber circuits electrically connected in parallel withthe plurality of thyristors, respectively, between the different pairsof the phase terminals.
 74. The surge protection system of claim 73,further comprising: a plurality of inductors electrically connected inseries with the parallel combinations of the plurality of thyristors andthe plurality of snubber circuits, respectively, between the differentpairs of the phase terminals.
 75. The surge protection system of claim74, wherein each of the plurality of inductors comprises: anelectrically conductive coil member, the coil member including aspirally extending coil strip defining a spiral coil channel; and anelectrically insulating casing including a separator wall portion thatfills the coil channel.
 76. The surge protection system of claim 22,further comprising: a housing that includes a cover defining an enclosedcavity; wherein the crowbar device and the plurality of surge protectiondevices are within the housing; and wherein the housing includes afiller material that at least partially fills a volume enclosed cavitynot occupied by the crowbar device and the plurality of surge protectiondevices.
 77. The surge protection system of claim 22, wherein thecrowbar device is electrically connected to an external current sensor.78. The surge protection system of claim 22, further comprising: anexternal trigger and alarm interface circuit electrically connected tothe crowbar device.
 79. The crowbar system of claim 72, wherein thecrowbar module is coupled to and between a plurality of phase lines andis configured to prevent an overvoltage condition by selectivelygenerating a low resistance current path between the plurality of phaselines.
 80. The crowbar system of claim 79, wherein the thyristor isconnected between a pair of the plurality of phase lines.
 81. Thecrowbar system of claim 79, wherein the trigger circuit is configured togenerate a thyristor trigger signal responsive to detecting a faultcondition on the pair of the plurality of phase lines, the thyristorbeing responsive to the thyristor trigger signal.
 82. The crowbar systemof claim 79, wherein the trigger circuit comprises: a rectificationcircuit that generates a direct current (DC) signal corresponding tovoltages between the plurality of phase lines; a comparator thatcompares the DC signal from the rectification circuit to a referencesignal; and a plurality of isolation drivers that receive a comparatoroutput, and, responsive to the comparator output indicating that the DCsignal exceeds the reference signal, generates a trigger signal thatturns on the plurality of thyristors.
 83. The crowbar system of claim72, wherein the crowbar module is electrically connected to an externalcurrent sensor.
 84. The crowbar system of claim 72, wherein the externaltrigger and alarm interface circuit is configured to provide aconnection between the trigger circuit and a monitoring location. 85.The crowbar system of claim 84, further comprising: a microcontrollerconnected between the trigger circuit and the external trigger and alarminterface circuit; wherein the microcontroller is configured to send analarm signal and/or supervisory control and data acquisition (SCADA)information to the monitoring location.
 86. The crowbar system of claim85, wherein the monitoring location comprises a remote visual and/oraudible annunciator.